This was the first Discworld game released (IIRC), for the Sinclair ZX Spectrum. Luckily, through the miracle of technology, the game is available here for your enjoyment. However, you'll have to download an emulator to play it!
The Colour of Magic Game - zip file
A good Spectrum emulator - zip file
Walkthrough
For help with zip files, click here.
Copyright © Terry Pratchett from the Discworld (R) Novels. Maintained by Jennie Lees, lees@mistral.co.uk - 1998.