The trichromatic theory of color vision

Written by s.l. stoddart
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The trichromatic theory of color vision

The trichromatic theory of colour vision explains how humans are able to view different colours. Years of research have provided information on how the human eye deciphers colours. While the trichromatic theory successfully explains how colour vision works, it has also been the basis for additional theories that attempt to further explain how the brain receives colour images.


According to the Encyclopedia Britannica, the trichromatic theory was first proposed around 1801 by the English physician Thomas Young, then refined about 50 years later by the German scientist Hermann von Helmholtz. Young first proposed that colour vision was the result of the action of three different colour receptors. Helmholtz later discovered that three wavelengths of light were needed to create different colours.


According to the Encyclopedia Britannica, experiments were performed that allowed participants to manipulate light. Participants were given a colour sample to match by altering three different wavelengths of light. Results from the experiment show that when two wavelengths were used, the colours could not be matched. However, when three wavelengths were used, the colour could be matched.

Cone Cells

It was not until 1965 that groundbreaking research revealed that there are three types of colour-sensitive cones in the retina of the human eye that correspond to red, green and blue sensitive detectors. According to Georgia State University, 64 per cent of the cones in the eye are red-sensitive, about 32 per cent are green sensitive and roughly 2 per cent are blue sensitive. Blue sensitive cones have the highest sensitivity, while red sensitive cones have the lowest sensitivity.


The results from many experiments led to the formation of the Young-Helmholtz theory of colour vision. This theory states that three receptors in the retina of the eye are responsible for the perception of colour by the brain. Each receptor is sensitive to a single colour: red, green or blue. The combination of these three colours can form any visible colour in the spectrum. This theory is more commonly known as the trichromatic theory of colour vision.

Colour Blindness

This theory paved the way to understanding colour blindness. According to the Encyclopedia Britannica, the existence of several kinds of colour blindness can be explained as the lack of function of one or more sets of the cones. If one set of cones is not operating correctly, dichromatism occurs (also known as partial colour blindness). In rarer circumstances, an individual can suffer from monochromatism, or complete colour blindness, if there is no functioning cone system.

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