Colour perception

Colour vision is a complex science, and I’m not doing more here than highlight a few things I’ve found important for information designers.

Firstly, if you’re planning to use colour coding, there’s a limit to the number of colours you can use. Although the human eye can distinguish millions of shades, we only have around ten basic names for them (in English) before we start having to move to subordinate terms such as mint green or light blue. Think of the colours you find in a child’s set of crayons. We have green, yellow, orange, red, purple, blue, black, white, grey, and brown. We can perhaps add magenta, pink, beige, turquoise, lime and navy.

This linguistic evidence is a clue as to how many colours we can reliably remember when faced with a colour coding system.

A related point is that the background affects our perception of colour. Here are two purple squares. If we then put one of them on a black background it’s hard to tell which one it is.

Some colour-background combinations should be avoided altogether. For example, green+red causes a shimmering effect (there’s a scientific explanation I won’t attempt).

Finally, we have to watch we don’t make vital distinctions using colours which colour blind people confuse. 8% of males have a problem distinguishing red from green (most other conditions are very rare). Many are mildly affected, but some would struggle to see the differences in the rows below:

You can use a second coding system to compensate – for example, traffic lights use position as well as colour to distinguish stop from go. This is known as redundancy.

Everyone should read the classic Interaction of Color, by Josef Albers.¹

1. Josef Albers (1963) Interaction of color, Yale University Press

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