Young-Helmholtz three-colour theory

The Young-Helmholtz three-colour theory, also known as the trichromatic theory, proposes that human color vision relies on three types of cone cells in the retina, each sensitive to different parts of the light spectrum. These cones are preferentially stimulated by red, green, and blue light, respectively.1

When light of a particular color strikes the retina, it stimulates these three cone types to varying degrees. The brain interprets the combined signals from these cones to perceive a specific color. For example, yellow light would strongly stimulate the red and green cones, but minimally stimulate the blue cones, resulting in the perception of yellow. This theory explains how a wide range of colors can be perceived from a limited number of photoreceptor types and accounts for color mixing phenomena.12