The Human Eye Can Distinguish Around 10 Million Colours

Three Types of Cone

Human colour vision relies on three types of cone cells in the retina, each sensitive to different wavelengths of light: S-cones (short wavelengths — blue), M-cones (medium — green), and L-cones (long — red). Colour perception arises from the brain comparing the relative activation of these three cone types.

Given roughly 100 distinguishable levels of intensity for each cone type, the combinatorial maths yields approximately 100 × 100 × 100 = 10 million discriminable colours.

Tetrachromacy: Seeing Even More

Most humans are trichromats — three cone types. But some people, almost exclusively women, carry a genetic mutation giving them a fourth cone type. These tetrachromats may be able to distinguish up to 100 million colours. Artist Concetta Antico is one of the most studied cases — she describes seeing colours in shadows and in bark that most people simply cannot perceive.

A tetrachromat looking at a rainbow sees it as composed of dozens of distinct bands invisible to ordinary vision.

The Words We're Missing

English has names for only a tiny fraction of the colours we can see. Researchers have found that language shapes colour perception — languages with more colour words produce speakers who are faster and more accurate at distinguishing shades. The Russian language, for example, has separate basic terms for light blue (goluboy) and dark blue (siniy), and Russian speakers consistently perceive these as more distinct than English speakers do.