That was his first introduction to the tertiary colours, the colours on the far side of blackness, the colours that you get if you split blackness with an eight-sided prism. They are also almost impossible to describe in a non-magical environment, but if someone were to try they’d probably start by telling you to smoke something illegal and take a good look at a starling’s wing.

Terry Pratchett – Pyramids – c.1988,2011