Glazes   

A thin, transparent layer of paint. Glazes are used in layers, one on top of another to build up depth and modify colours in a painting. A glaze must be completely dry before another is applied on top.

Impasto

A thick, textured application of paint where the marks made by the brush or painting knife remain visible, such as in the work of Vincent van Gogh.

Wash

A watercolour term for a flat layer of very diluted colour laid across the paper. It can either be an even layer of colour or a graded layer which gets lighter.

Tint 

Any colour that has been mixed with white. In watercolour, this is achieved by adding more water, thus allowing more of the paper to show through.

Hue

The actual colour of something, such as red, green, or blue. What we generally, but less technically correct, call colour.

Primary colour

One of the three colours - red, yellow, and blue - that cannot be created by mixing other colours.

Secondary colours

A colour made by mixing two primary colours together: red and yellow to get orange, yellow and blue to get green, or red and blue to get purple. The secondary colour depends on the proportion in which you mix the two primaries. For example, if you add more red than yellow, you get a reddish orange, and if you add more yellow than red, you get a yellowish orange.

Tertiary colours

Neutral colours, such as browns and greys, containing all three primary colours. They're created by mixing either all three primary colours or a primary and secondary colour (secondary colours of course being made from two primaries). By varying the proportions of each primary colour, you create the different tertiary colours.

Tone

The lightness or darkness of a colour, rather than what the actual colour is.

Adjacent colours

Quite literally, the colour next to another on the colour wheel.

Complementary colours

Two colours on opposite sides of the colour wheel, which when placed next to each other make both appear brighter. The complementary colour of a primary colour (red, blue, and yellow) is the colour you get by mixing the other two (red + blue = purple; blue + yellow = green; red + yellow = orange). So the complementary colour for red is green, for blue it's orange, and for yellow it's purple.

Palette

The word palette usually means the surface on which artists lay out and mix their colours. It may also refer to the range of colours an artist works with.

Medium

The substance that binds the pigment (colour) in paint. In acrylic paints, this is a synthetic substance. (In oil paints, it's a natural oil such as poppy. In tempera, it's egg yolks.)