mixing green

There are three reasons why green is a difficult colour for many artists.

Green is, first of all, the colour that is most difficult to identify accurately. People vary considerably in their choice of a "pure" green colour, have difficulty distinguishing one green colour from another, and have few specific "green" colour labels to identify and remember green colours. As a result, our perception of green is more likely to be a "colour idea" — the green we think a lawn or a leaf should be — rather than the green that matches the actual visual sensation. Foliage greens, for example, are typically much darker and duller than we remember them.

When we go to mix paints, we find it's difficult to pick the right paint combination — blue and yellow, or green and yellow, or green and blue — to get the right shade of green, because green mixtures are different from other mixtures. In particular, they follow curves rather than straight lines across a colour wheel. These mixing complications are the reason there are so many premixed convenience green paints on the market.

Finally, green is a difficult colour to harmonize in a painting. Green (like purple) has a powerful tendency to overwhelm a painting, even when used sparingly — something that 19th century watercolorists often lamented.

the green mixing system

There is a basic system for mixing greens. All painters learn this system and how to use it to get the greens they want. Unfortunately, it is hard to see the basics of green mixtures behind "primary" colour dogmas and colour wheel simplifications. So we begin by focusing on the green mixing system. Once we understand this system clearly, we can look at green mixing recipes and the common problems with green mixtures.  

Basics of Green Mixing. Let's start with a fundamental rule of mixing greens: green mixtures require three paints. A tube paint by itself isn't enough, and typically a mixture of two paints is insufficient too.

The three necessary paints are:

·   a yellow paint, which can range from a green gold to a deep yellow (the paint cannot be orange, as orange is a mixing complement of green blue and therefore will not mix a green colour with a blue paint);

·   a green or blue paint, which can range from a deep blue (ultramarine blue) to any single pigment or convenience yellow green;

·   a neutralizing paint, which can be a black paint or any colour from orange to violet, depending on the hue of the green mixture.

Many artists use a premixed or convenience green in place of a yellow+blue or yellow+green mixture, but they still require a second paint to shift the green lightness, chroma or hue in different painting situations.

This diagram shows how these different paints fit together on the artist's colour wheel.

To adjust the chroma of this mixing line toward gray, or to make the yellow warmer and darker, a small amount of the third paint, the neutralizing colour, is added.

All these mixtures can of course be lightened with water or white paint, and darkened with a black or dark neutral paint or the green's mixing complement.

There seems to be a missing possibility: what about brightening the mixture with an added green paint? In practice, artists rarely mix greens this way. The greens that are most effective in a painting are usually rather dull — certainly duller than it is possible to mix with paints. So artists choose the basic convenience green, or mixed yellow+blue or yellow+green mixing line, to define the most intense green that will work in a particular painting. The neutralizing adjustments dull and warm this green or range of greens as needed.

Five Basic Green Mixtures. The green mixing system defines five basic types of subtractive green mixture. The reflectance curves at right show what happens "under the hood" in each case:

(1) green+yellow. The mixture of a green and yellow paint produces a distinct peak of "green" reflectance, and an elevated "red" reflectance with darkened "blue" reflectance. It resembles the reflectance curve of lawn grass or "vivid" yellow greens; the "red" reflectance increases the chroma of the green and shifts its hue to toward yellow. In the gamut of artists' paints, this is perceptually the most luminous (intense and light valued) green, and it is a very warm green as well.

(2) blue+green. The mixture of a blue and yellow paint produces a distinct peak of "green" reflectance, and an elevated "blue" reflectance with darkened "red" reflectance. The is the darkest and coldest green.

(3) blue+yellow. The mixture of a blue and yellow paint produces a subdued peak of "green" reflectance and a raised "red" reflectance, which shifts the hue toward dull yellow; these are excellent landscape greens because the mixture proportions of yellow to blue can be used to match the balance between orange and blue that defines the colour of light.

(4) green+warm. The mixture of a middle green with a near neutralizing warm (red or orange) paint — in the example, the red orange burnt sienna — produces a somewhat less prominent "red" plateau and lowered "blue" reflectance. As more neutralizing paint is added the green becomes warmer and eventually reaches the warm boundary between green and red, matching green foliage lit by the red light of the setting sun.

(5) green+complement. The mixture of a green and its mixing complement, which can be anything from a scarlet to purple, depending on the hue of the green and the depth of dark or gray desired. This produces a wavy or bumpy neutral profile, which to my eye gives greys mixed from green and magenta a unique and subtle lustre, especially when the colours are mixed unevenly (wet in wet) or are contrasted in pigment texture.

The point is that the choice of paints used to mix the green inevitably starts the green in a specific direction — warmer, colder, more luminous, darker or more subdued. This is not a characteristic of a specific green hue or single paint, but a characteristic of the specific combination of pigments that are used to make the green mixture. This chart summarizes the basic mixing dynamics of these combinations.

green mixing recipes

As we’re interested in the variety of green paint mixtures, we need a basic framework or conceptual map that can put all the these greens in a larger context. Rather than just "mix a lot of greens," willynilly as the experts advise, we want to see how our mixtures fit into overall hue circle, in order to guide our attention, direct our explorations and help us to useful conclusions. We will use the artist's colour wheel, which shows the hue and chroma location of all common watercolour pigments.

Overview of Paint Choices. The number of paints choices is large and confusing, so we need a way to simplify the mixing alternatives. We divide the colour wheel into sections, and assume the paints within each section produce comparable mixing results. As the figure below shows, the paint colours available to mix greens are essentially green itself, plus yellow and blue. In the diagram below, these are divided into a "warm" and "cool" hues, to produce six hue categories. These paints span more than half the visual hue circle.

There are still many differences among paints in the same hue category, such as lightness, transparency, staining and texture. But the difference between saturated and unsaturated paints has the greatest effect on the saturation (intensity) of the colour mixtures. So within each of the six hue categories, we can separate single pigment paints into two groups: those with the highest chroma for that hue, and those paints that are duller.

In either case, the true colour does not appear until the paint has completely dried. If colour control is essential, there are two solutions: (1) make test paintouts on a scrap piece of paper, and let dry, to judge the mixture; (2) paint the cadmium yellow first, as a foundation layer, then glaze the green or blue paint over it. Because the phthalo colours (green and blue) are the most transparent watercolour pigments available, this method works very well.

Another problem is that you must have a delicate but confident touch. Especially when used in concentrated mixtures, the cadmiums must be laid down without fussing. Rebrushing or retouching a passage of cadmium paint while it is still wet can quickly dull the dried colour, producing an effect like scuffed velvet. When applied wet in wet, the cadmiums produce a lovely, powdery mist of colour, and their weight, active diffusion and opacity usually causes them to separate slightly from other pigments if applied in juicy brushstrokes or wet in wet (especially in backruns), producing interesting and expressive pigment effects.

All things equal, the bright green mixtures created by cadmium lemon (or cadmium yellow pale) offset any difficulties. For that reason it's much more common for artists to use a greenish rather than a reddish cadmium in their palettes.

If highly saturated colour is what you're after, be aware that, regardless of pigment, the most saturated yellows are middle rather than lemon hues. For example, the chroma of a good middle cadmium yellow is at or above 97, while the average chroma of a cadmium lemon is only 91. (The same difference appears in the synthetic organic yellows, for example between hansa yellow light, with a chroma of 90, and hansa yellow, with a chroma of 99 or 100.) So, even though the middle yellow contains "more red" or is "warmer" (in the wacky world of the "split primary" colour theory), it can actually mix greens as saturated as a cadmium lemon!

(2) Weaving through the span of cadmium hues is a group of saturated synthetic organic yellows, including the arylide (hansa) and benzimidazolone paints, plus a few exotics such as anthrapyramidine yellow (PY108), isoindolinone yellow (PY110) and quinophthalone yellow (PY138). In terms of the range of mixed greens they create, these pigments are almost indistinguishable from the cadmiums, and they typically cost less.

Compared to the cadmiums, there are several differences in their mixing behaviour: they are more transparent and typically have a lower tinting strength and are more sensitive to backruns; they tend to lose colour more in tints. Most will not separate if mixed with the phthalocyanines and applied in juicy wash, so you have better control of the finished hue as you mix it.

In my experience, the most saturated yellow available in watercolours is the arylide pigment hansa yellow (PY97), which is also remarkably lightfast and semitransparent as well (it used to be marketed by Winsor & Newton as "transparent yellow"). It's one of the most commonly used yellows in convenience green paints for those reasons. It's really worth your while, whatever choice of paints you now use or plan to explore, to look at this pigment. The benzimidazolone yellows (PY151, PY154 and PY175) are also worth looking at, although their lighter value causes them to have a slightly lower chroma.

(3) The third major group is the metal yellows, which include green gold (copper azomethine yellow, PY117 or PY129), nickel azomethine yellow (PG10 or PY150), and nickel dioxine yellow (PY153). The azomethines are the most transparent yellow pigments available, have good tinting strength (unless the watercolour brand has reduced the pigment load), and have a slightly unsaturated (brownish or greenish) colour and a slightly granular texture in masstone. All the paints show a strong colour shift (toward green) from masstone to tints.

In terms of its colour, transparency and hue shifts, the recently expired quinacridone gold (PO49) can also be included in this group. Like hansa yellow, it was very often used in convenience green paints, and produces mellow, transparent and pleasingly dark yellow green mixtures.

These paints are exceptionally good in landscape work, especially when mixed with transparent blues or greens such as the phthalocyanines or iron blue (PB27). As they tend to be on the warm side of the yellow range (which causes them to make less saturated mixtures with green or blue pigments), their unsaturated colour isn't objectionable. It turns out to be a benefit: these yellows mix the most natural, consistent and muted range of yellow greens you can get, and the lightfastness of the mixtures is very good. The transparency offsets the lack of saturation: the mixed greens are duller, but also cleaner looking and easier to handle.

(4) The last group of yellow pigments is the diverse earth yellows, including yellow ochre (PY43), raw sienna (PBr7), raw umber (PBr7) and gold ochre or transparent yellow oxide (PY42).

The earth pigments can mix very natural greens, but some (gold ochre and yellow ochre) tend to make opaque or dull mixtures and, like the cadmiums, will separate if used in juicy applications with the phthalocyanines. As with the cadmiums, the cure is to glaze the darker paint over the earth yellow applied as a foundation, or to mix earth greens with similarly textured cobalt green or cobalt cerulean paints. (These mixtures must be used in diluted, juicy washes, as they will appear unreflective in masstone, and will muddy if fussed with after they are applied.)

I've excluded from consideration the opaque and whitish titanium metal complex yellows — nickel titanate yellow (PY53), chrome titanate yellow (PBr24) and Winsor & Newton's turner's yellow [hue] (PY216) — pigments originally developed for applications such as aluminium siding and ceramics. These titanium based paints are less satisfactory because they add a whitened lustre to any green mixture that does not much resemble vegetable greens, though they might be apt to render desert adapted plants such as yucca, palm or aloe.

The earth paints are cheap and reliable, but I find that the combination of unsaturated colour and opaque texture is difficult to manage: the finished colour often looks flat and heavy. Convenience greens made with phthalocyanines and iron oxides suffer the same problems and should be left to "student" grades of paint.  

Greens. In terms of saturated, strongly tinting and completely lightfast pigments, the greens, blues and violets are the impoverished sections of the colour wheel. Not only are the available pigments in these hues rather unsaturated — there are relatively few of them. They form three distinct groups:

(1) The major class of green pigments is indisputably the phthalocyanines, which come in two hues: phthalocyanine green BS (blue shade, PG7) and phthalocyanine green YS (yellow shade, PG36). Although relatively dark valued (the blue shade is darker than the yellow), these are strongly tinting, strongly staining, moderately saturated and very lightfast pigments. Almost every artist's palette I know of includes one of the phthalo greens or a convenience mixture made from them.

The most saturated and darkest green mixtures possible combine a saturated yellow with a phthalocyanine green paint. The phthalocyanines provide the maximum colour saturation and maximum value range possible in a green mixture. The phthalocyanines are also transparent and have a perfectly liquid texture. They define the chroma and darkness limits of what you can do in green mixtures.

Main concerns with the phthalos: a strong tendency to stain and high tinting strength. The staining is a plus if you use the phthalos as a foundation that you glaze over with a colour you want to lift away. For example, if you glaze over a phthalo paint with a cadmium yellow, you can lift away the cadmium (by wetting and blotting) to reveal areas of green within the colour field. (Jim Kosvanec's claim that the phthalos will "stain" the opaque cadmiums and give you "mud" depends on how the paints are used.)

The high tinting strength simply means — use with caution! It's very easy to overwhelm a mixture with what seems like a tiny amount of phthalo paint, especially when the phthalo is only moderately diluted. My rule is, choose the amount you think is correct to add to a mixture, then add one third of that to start.

Because of their very fine particle size and low specific gravity, the phthalos easily separate from heavy (cobalt blues, earth yellows) or opaque (cadmium yellow, bismuth yellow) pigments in juicy mixtures. The best remedy, as described above, is to put down the yellow colour first, let it dry completely, then glaze the green or blue phthalocyanine on top. But the pigment separation can produce interesting and attractive patterns and variations in the colour area.

Besides the steroid phthalos, there is a handful of granulating, rather opaque and unsaturated cobalt and chromium pigments.

(2) There are two chromium greens. Viridian (hydrous chromium sesquioxide, PG18) is a traditional green the exact same hue as phthalo green BS — but usually granulating, nonstaining, and slightly less saturated and lighter valued. It is much weaker in mixtures, even with iron oxide yellows. Some artists prefer it because it mixes more natural (slightly dull) greens, and is much easier to lift or correct if needed. It works especially well with cadmium paints of any hue; it makes a lovely iridescent gray with most cadmium reds.

The sleeper is chromium oxide green (anhydrous chromium sesquioxide, PG17), a very dull yellowish green close to the hue of many sap greens (it is commonly used in camouflage paints). Unlike mixed sap greens, however, it is very opaque. In very diluted mixtures it creates a hazy, delicate texture and is quite effective at creating a wide range of natural, warm, muted greens when added in small amounts to any yellow pigment. Its opacity also lends substance to green passages that should appear heavy. If you have struggled to get natural looking landscape greens using the phthalocyanines, I urge you to give chromium oxide green a try (or viridian, for that matter). Just remember: the semitransparent viridian can be applied in fairly heavy concentrations, but the very opaque chromium oxide green works best in diluted mixtures or added to mixtures in small amounts.

(3) Finally, the green cobalts. Cobalt green comes in a few different flavours (PG19, PG26 and PG50): all are semiopaque, unsaturated, granulating, weak in mixtures, and very sedimentary. (Cobalt teal blue, PG50, because of its light value, mixes surprisingly bright yellow greens.) If you mix these with cadmium or earth pigments, keep the mixture well diluted — otherwise you really will get a dull colour.

The cobalts work best with the synthetic organic or metal yellows, but tend to sludge over these pigments in juicy applications, shifting the mixed hue toward a green. Probably the most acceptable are the cobalt titanium greens (PG50), which also come in a blue and yellow shade. But their whitish colour limits the value range of the mixed hues, and they separate from the yellows as well. I find them hard to work with.

You may also run across paints labelled terre verte or green earth. If these really are earth pigments, rather than hue substitutes made from chromium or cobalt pigments, they are more often used in portrait than in landscape work, as a foundation colour to render facial planes that are shadowed or obliquely lit. They are usually very weakly tinting, dull, transparent, and moderately light valued.  

Blues. The blue pigments can also be classified into three groups:

(1) As with the greens, the major pigment class of blue pigments is the phthalocyanines — which come in a broader range of shades, from phthalo turquoise (PB16), phthalo cyan (PB17), phthalo blue GS (green shade, PB15:3), and phthalo blue RS (red shade, PB15:1). (Phthalos without the red/green distinction tend toward the red end of the colour range: see the colour chart displayed under phthalo blue.) Because of its dark value, tinting strength, transparency and staining, iron (prussian) blue (PB27) should be included in this group as well.

All the previous comments under the phthalo greens apply to these blues as well. Although relatively dark valued, these are strongly tinting, strongly staining, and moderately unsaturated colours. The pigments have a very low specific gravity and extremely small particle size, so they are unusually susceptible to backruns and diffusion wet in wet. The chroma of these paints increases as they are diluted up to a middle value, producing lovely bright tints that are unusually good as sky colours. Iron blue in particular mixes evocative dark greens, especially in landscapes, and is not as saturated as the phthalos and therefore mixes more subdued shadow purples. Its one drawback is that it is occasionally less lightfast in tints. The choice between a phthalo or iron blue is primarily one of mood and delicacy of colour, especially if the same blue is used for landscape greens and skies. All are valuable to explore and to have on your palette.

(2) Overlapping the hue range of the phthalocyanines is the second category of blues, the many cobalt pigments. Cobalts start out fairly saturated in the blue violet or reddish blue hues (PB73 and PB28), but decline in saturation as the hue shifts toward turquoise because of increasing amounts of chromium. (See the colour chart under cerulean blue PB36, and the hue and saturation positions of the cobalts in the artist's colour wheel.)

In the "colour theory" explanation of the "split primary" palette, a greenish blue pigment should mix (with yellow) more saturated greens than a reddish blue. But in the cobalts this simplistic rule breaks down. The decreasing saturation in the greener cobalts counteracts the increase in the green hue; the different cerulean and turquoise cobalts mix very similar, unsaturated, granulating greens.

Cobalt teal blue (PG50) , at the boundary between green and blue, is the exception. It has the same hue as cobalt turquoise but is somewhat more saturated because of the whitening effect of titanium. It produces somewhat more saturated green mixtures than the other cobalts, although it can't achieve a very dark value. Like the titanium yellows, it tends to add a whitened lustre to mixed colours. It is however very effective as a foundation wash, glazed over by darker deep blue paints, to give skies a glowing middle blue hue.

All the cobalts are granulating and semiopaque, which opens up interesting artistic effects but also makes the paints more troublesome to mix and apply without the colours separating on the page.

(3) The last group of blue pigments is a handful of unique pigments: manganese blue (PB33, ultramarine blue (PB29) and indanthrone blue (PB60).

You're unlikely to use the first of these blues. Manganese blue is difficult to obtain, highly polluting to manufacture, strongly granulating, and usually packaged with a gummy vehicle. (Personally, I love the stuff for its colour and texture in landscape washes and portraits, but it has never been very popular.)

Ultramarine and indanthrone blue are quite dark, relatively saturated red blues, and they are valuable for mixing dark greens very close to gray — pine trees seen in the distance, or eucalyptus trees in a haze. Neither one makes a very good dark pigment: ultramarine blue is too saturated, and indanthrone blue tends to have a whitish sheen. They will mix to green with any yellow pigment up to benzimidazolone orange (PO62). But they are not essential: nickel azo yellow and phthalo blue, with a touch of quinacridone rose, will mix equally effective transparent, dark greens.

green mixing problems

There are several specific problems with mixing greens that need to be discussed separately from the mixing system and the "colours" that make it work.  

Green Value & Chroma. Context is the main reason why a green mixture recipe by itself is not going to get you to a satisfactory green or confident mastery of green mixtures. Confusion often arises from the idea that "colour" exists separate from context.

Asking the question "what is a good green mixture?" is like asking "what is a good green chair?" After all, you want the green chair to fit in with everything else in your room, but usually any random green chair is going to clash with other colours in the room.

Friends recommend this or that green chair, and after trying several out you go, "aha, here is the green chair I've been looking for!" and the room you put it in looks great. But there are many rooms in your house, so now you go to a different room — different colour scheme, more light, different side of the house — and the same chair looks wrong again. Darn it! You have to start looking for green chairs all over again.

In this anecdote the green chairs are different paint mixture recipes for a "good green," and the different rooms are different landscapes, different botanicals, different painting contexts in which the green mixture appears.

The basic problem is that green must represents three different visual facts at the same time. It represents a value or lightness in your value scheme, determined by the amount of light shining on it; it represents a surface colour that depends on the concentration of chlorophyll in a specific type of plant (an oak green is different from a maple green; grass green is different from cactus green, etc.); and it represents a mixture of light and surface colour that reveals the brightness and hue of the ambient light. Just "finding a good green mixture" means you must paint all these visual facts the same way.

The solution for the value scheme problem is to examine the sequence of greens from lightest valued to darkest, and paint them in order from one extreme to the other, systematically increasing or decreasing the concentration of green paint in water. Do this with any reasonably dark, middle green paint or mixture, in the same way you would lay down the value scheme using a black paint: dilute the paint for lighter values, and below its masstone value add black or a complement to darken it further.

Once you get the value relationships approximately right, look next at the hue. Then render hue by glazing over the foundation colour with a transparent yellow or blue paint. This will darken the colour somewhat — more for the blue than for the yellow, which will slightly increase the value range.

Another approach is to use a bright or "neon" green, such as Daniel Smith's phthalo yellow green or Rowney's vivid green, and paint in all greens with that paint to start, then let the greens completely dry. This puts the green far into the light values and yellow hue bias. Most of the greens will be screamingly wrong no matter what it is you are painting. But they will be so wrong that you will easily see what is wrong — they need to be dulled with quin gold, or burnt sienna, or quin magenta, or shifted toward blue with dioxazine purple, or phthalo blue, or phthalo blue green — and this process helps you understand how to see and adjust hue differences.

Adjusting hue and value usually dulls the green to approximately the right chroma, but if the green is still to intense, then glazing over with a diluted mixture of the green's mixing complement will get it right.  

Foliage Greens. Once you have a basic green painting approach, the next hurdle is overcoming the "colour idea" that prevents you from accurately seeing the foliage green you want to paint. To break out of that conceptual box, it helps to locate foliage greens in the CIELAB colour space, the same space where we've mapped the mixing lines.

The figure shows the visual colour wheel with the hues ranging from 100% saturation or 100% brightness along the rim to 0% saturation or brightness (black) at the centre. The background colour tiles decline in brightness and saturation in 20% steps.

Superimposed on the wheel are the approximate hue and saturation positions for the leaves of a variety of common plants and trees — dead and alive — as sampled from colour digital photos taken in early afternoon light (in California, USA during May).

These include the greens of most deciduous trees, flowering plants, lawns and, at the extreme, those young shoots that are so brilliant and distinctive in early spring.

An easy way to remember the location of natural greens is that they mostly fall along a line drawn parallel to the "primary" yellow (vertical) spoke of the colour wheel (roughly from the tiles for "japanese box hedge" to "eucalyptus" in the figure) but shifted halfway toward colour point 12 (permanent green light). The result is that from yellow green to blue green, greens darken and lose saturation. In florals or landscapes, the blue greens will typically appear darker and duller than the yellow greens.

The green and blue versions of phthalocyanine green (shown in the diagram) are too saturated. There are very few natural greens the colour of either phthalo pigment by itself. We cannot readily use these colours without modifying them, which throws us back on the difficult task of hitting the natural colours through a mixture.

This distribution of greens also suggests why it is so hard to hit a natural green by a mixing yellow with a green or blue pigment: the yellow to green/blue mixing lines (shown in the previous diagram) run horizontally, while the spread of natural greens runs vertically. It's like pitching horseshoes: it's easy to undershoot (too yellow) or overshoot (too green) the goal.

This is why paints such as sap green are so popular, even among artists who otherwise only use single pigment paints. It lies in the centre of the natural green distribution — no worries about hitting the colour exactly. Added yellow takes the colour toward new deciduous leaves, added blue violet takes it toward pine or olive, added phthalo green takes it toward geranium. It radiates natural greens in all directions.

Many artists underutilize the warm mixing potential of sap green. Combined with quinacridone rose, burnt sienna or benzimidazolone orange (PO62), sap green mixes lovely muted browns, tans and olive greens, the colour of parched, dried or dead leaves. It can generate both the living and dead colours of plants and trees.  

Green Bias and Daylight. Understanding the basic surface colour of vegetable greens is a good start, but these greens mix subtractively with the colour of the light falling on them, and they appear to shift in hue — from blue toward yellow — as the intensity of incident illumination increases. So you need to understand how greens behave as the light around them changes.

The common types of landscape illumination are the phases of daylight, which include changes in total light from noon to darkness, and the contrast between lighted and shadowed surfaces. The two standard illuminants used to study these effects are: (1) daylight at one hour before sunset, which produces a deep yellow or orange light (CIE illuminant A); and (2) daylight at noon, which produces a bluish and intensely bright light (CIE illuminant D65). Note that both the intensity of light and its colour are in play.

Greens are the "curve ball" in colour mixing. But these curved colour paths are only the surface symptoms of other subtle and complex problems that turn up when making green mixtures:

• Rapid colour change. As yellows are mixed with a blue or green paint, they quickly darken and shift clockwise on the colour wheel. As a result, the mixture seems to shift suddenly toward a middle green. As blues are mixed with a yellow paint, the darker value of the blue makes it dominate the mixture, pulling the colour toward a blue green. Then, when the mixed colour has dried, it becomes significantly lighter valued and less intense. (The overall drying shift can be as large as 30% to 50% of the wet mixture's lightness, chroma and hue.) So the mixture on the palette is always very different from the dried colour on the paper. These problems are the primary reason why green mixtures seem uncontrollable, and why intense, "yellow" greens or rich dark greens are so difficult to mix accurately. The remedy is to slow down and treat mixed greens with more attention: you will learn to compensate for these problems more quickly.

• "Yellow" greens. Yellow turns into an apparent green — usually a light valued, olive or golden green — while the hue of the colour is still actually yellow (as shown by the green boundary in the figure). In fact, an unsaturated green colour is easily made by mixing a lemon or middle yellow with a touch of black pigment, which shifts the colour straight toward the centre of the wheel. (Dull, dark chromium oxide green works on yellows in a similar way, and produces lively but delicate greenish yellows and leaf greens.) These green golds are within the unsaturated colour zone for yellow, but seem to be on the green side of the colour wheel. This again makes accurate mixing difficult: we may try to get these colours by mixing yellow with a touch of green, but the result will be too green.

• Desaturating warm shift. Many artists use a dull scarlet or orange paint, such as burnt sienna (PBr7), to desaturate their green mixtures (shift them closer to gray). But these colours actually shift the green hue back toward yellow as much as or more than they shift it toward the neutral centre of the wheel, resulting in a yellowish green colour. The best paints for desaturating green mixtures straight toward gray are much bluer, such as dioxazine violet (PV23) for a yellow green, and quinacridone carmine (PR N/A) for a blue green. Of course, if a warm shift is the effect you want, then a transparent red iron oxide or burnt sienna is ideal.

• Blues for blue green. Even though phthalo green BS is a very bluish green, it's often a poor choice for mixing blue greens. The reason: it's too saturated. As with the dull greens tucked under saturated yellow, there are dull blue greens hidden under saturated blue green. You can't reach these evocative blue greens by mixing phthalo green and a yellow paint. Use the phthalo greens to mix yellow greens: blue greens should either be mixed with a yellow and blue paint — phthalo cyan, phthalo blue, cerulean blue, or ultramarine blue — or by dulling phthalo green BS with one of its many scarlet or red mixing complements.

• Phthalos light and dark. It's common to think of the phthalo greens as differing in hue — yellow and blue shade. The key difference, however, is in value. Mixed with light yellow, the two shades of phthalo green produce very similar trajectories across the colour wheel; their hue differences don't matter much in the saturation of their mixtures. But phthalo green YS (PG36) creates saturated mixtures in a higher key (lighter values), while phthalo green BS (PG7) produces darker values and a greater value range overall. Use phthalo green YS if you must mix light valued, saturated greens (spring shoots, banana leaves, parrots), but try phthalo green BS for saturated darks (dark floral greens, rose leaves). A similar contrast applies in the choice between phthalo cyan (PB17) and phthalo blue GS (PB15:3).

What about the convenience greens? The CIELAB location of permanent green light and sap green (see diagram above) shows that they are roughly cantered within the fan of green mixing lines emanating from a bright or dull yellow. The benefit of these two convenience greens is that they reliably locate a specific hue, value and saturation of yellow green at a point where most yellow mixtures produce very similar colours. (Hooker's green and permanent green deep provide similar locations at a bluer hue point.)

Besides saving us the trouble of mixing the approximate yellow green we want, these convenience mixtures also make varying the green hues much simpler: we simply mix the convenience green with any other paint. Surprising as it sounds, olive green, sap green, permanent green or hooker's green are all located where added yellow, orange, red, magenta, violet, blue, blue green, earth colours, black or white will produce an interesting and distinctive new green shade. Expressive landscape or botanical painting can be reduced to liberal use of sap green, tweaked by random touches of whatever other colour suits your fancy, and complemented with specific mixtures of yellow and blue to provide other green accents.  

Finally, it's worth knowing that the mixing colour wheel attempts to fix this curvy business with mixed greens by scrunching the greens and blues closer together on one side of the wheel, as shown in the diagram (compare the visual and mixing wheels on this page).

The visual colour wheel does force you to work with curvy mixing lines — but this discipline leads to a much deeper understanding of how paint mixtures actually create new colours.

Matching Greens. The low saturation of many natural greens helps to explain why artists are typically content to put most of the saturation costs in their palettes on the green side of the colour wheel. Many artists omit a green paint from their palette entirely, mixing all their greens from whatever blues and yellows they normally include on their palette.

If you use a green, you probably will not need anything more than phthalocyanine green BS or phthalocyanine green YS for a green pigment, since these are darker and more saturated than most natural greens.

Once you have determined the colours you'll use, create a mixing step scale between the most saturated and greenest (lemon) yellow and the greenest blue (or green) on your palette: this defines the most saturated greens it's possible for you to mix.

It's worthwhile to do these mixing step scales for all combinations of yellows (including earths), greens and blues in your working palette. Paint these "green scales" on two sides of a piece of 600 GSM watercolour paper (or watercolour board) cut to a convenient size to use in the studio or carry in the field. These scales are useful to identify the best mixing approximation for any natural green hue: once you find a close match, you will know which two paints (in what proportions) give you the mixture. (These cards take a lot of mixing effort: I suggest you make two or three at a sitting, so you'll have a spare in case the other gets lost or damaged.)

Most of the difficulty is in deciding whether the green is a bluish green or a yellowish green; after that, the correct saturation is easy to get. Green mixtures from ultramarine blue (PB29) are usually close to gray, so the ultramarine "green scale" is useful for judging very unsaturated green mixtures.

Usually the green mixtures will be too saturated. Adding a little quinacridone rose or quinacridone violet (one bright, the other dark) will unsaturate most greens toward a light or dark gray.

Once you have mixed up the correct "base" green for a particular passage of foliage, there are usually three variations you can make on that green as you develop the painting:

1. Shadows will darken and desaturate the foliage greens, and also shift their colour temperature slightly towards blue. Shadows carry both the colour of the leaves and indirect illumination from the blue sky, and are lower in value because they receive less light. A foundation tint or glaze of ultramarine blue or dioxazine violet is usually sufficient to shift the "base green" toward these shadow colours.

2. On many plants (particularly in the bluish greens), the underside of the leaf is much lighter and less saturated than the side turned to the sun. This colour is often visible in moderate winds, which invert leaves to show the undercook. You can typically get this colour by taking the base green, unsaturating it with a transparent complementary colour, and applying the mixture as a tint.

3. Glossy dark leaves (such as rose leaves) will reflect the colour of the sky directly, and appear as a transparent middle blue with the dark base green visible behind it. To achieve this effect, first lay down a very light tint of the base green, then glaze with a light tint of ultramarine blue, or phthalo blue mixed with a little dioxazine violet (to make the blue warmer). Cobalt blues are too opaque and granular for this effect.

In general, greens can be very effectively mixed on the paper: wet the area with the base green mixture, then float in yellow, sienna, rose, violet or blue as needed to shape the foliage masses. Dry your brush and use it to wick up excess paint to lighten passages, or drop in some clear water. Trees and shrubs can be effectively shaped by adding the green in two or three layers — starting with the lightest, most yellow green, and putting the darkest, bluest green on last.

Last revised 08.01.2005 • © 2005 Bruce MacEvoy