Two complementary theories of color vision are the trichromatic theory and the opponent process theory. The trichromatic theory, or Young -- Helmholtz theory, proposed in the 19th century by Thomas Young and Hermann von Helmholtz, as mentioned above, states that the retina 's three types of cones are preferentially sensitive to blue, green, and red. Ewald Hering proposed the opponent process theory in 1872. It states that the visual system interprets color in an antagonistic way: red vs. green, blue vs. yellow, black vs. white. Both theories are now accepted as valid, describing different stages in visual physiology, visualized in the diagram on the right. Green ← → Magenta and Blue ← → Yellow are scales with mutually exclusive boundaries. In the same way that there can not exist a "slightly negative '' positive number, a single eye can not perceive a bluish - yellow or a reddish - green. (But such impossible colors can be perceived due to binocular rivalry.)
who proposed that the eye must have receptors for three colors of light
Thomas Young and Hermann von Helmholtz