Young-Helmholtz theory
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The Young-Helmholtz theory (proposed in the 19th century by Thomas Young and Hermann von Helmholtz) is a theory of trichromatic colour vision - the manner in which the photoreceptors in the eyes of humans and other primates work to enable color vision.
In 1802, Young postulated the existence of three types of photoreceptors (now known as cones) in the eye, each of which was particularly sensitive to a particular wavelength of the visible light spectrum.
Hermann von Helmholtz developed the theory further in 1850: that the three types of cone photoreceptors could be classified as short-preferring (blue), middle-preferring (green), and long-preferring (red), according to their response to the wavelengths of light striking the retina. The strength of the wavelengths detected by the three types of cones was then interpreted by the brain as a visible color.
The theory was proved over a century later in 1964, when microspectrophotopic readings of single eye cone cells were obtained.
