Ross Littlewood
Colour Vision
How light, cone cells and the brain work together—and why colour perception is not identical for everyone.
The essentials
Colour is a visual interpretation.
The retina contains cone cells with overlapping sensitivities to different parts of the visible spectrum. The brain compares their signals, along with brightness and context, to build our experience of colour.
Inherited colour vision differences are usually stable throughout life. A newly noticed or one-sided colour change may have another cause and should be discussed with an eye-care professional.
Read the complete guideEveryday design
Communicate beyond colour alone.
Add a second cue
Pair colour with a word, icon, shape, pattern or position so meaning remains clear.
Use strong contrast
Check the contrast between text and its background, not just the hue difference.
Test in context
Review charts, maps and interfaces in realistic lighting and on common devices.
About online colour tests
Online examples can illustrate a principle, but screens differ in colour calibration, brightness and viewing conditions. They cannot rule an eye condition in or out. If colour perception has changed, or a career assessment requires a formal standard, seek an appropriately administered test.