Nature's color palette explains why everything we see is a mix of red, yellow, green and blue

For centuries, biologists and linguists have puzzled over why humans consistently view and name colors using four pure hues: red, yellow, green and blue. These colors appear as distinct, opposed pairs: red and green; blue and yellow. Despite attempts to reconcile this with the three types of cone cells in our eyes that detect different wavelengths of light, the phenomenon remains unexplained.

Linguist Paul Kay and anthropologist Brent Berlin discovered that dozens of languages, including unwritten ones, categorize color based on these four hues, suggesting an innate aspect of human perception. Alexander Belsten, a postdoctoral fellow at Berkeley, and Bruno Olshausen, a neuroscientist, propose a theory that explains this conundrum.

They argue that the natural world, as opposed to the colorful human-created world, displays a limited palette of colors that our brain represents as combinations of just four pure hues. This explanation aligns with the idea that blue and yellow are opposites, as are red and green. The new theory reconciles two competing theories of color vision from the 19th century: Hermann von Helmholtz's theory of three receptor types and Ewald Hering's theory of four unique hues and their opponent nature.

Belsten and Olshausen's research indicates that while the retina detects physiological sensory mechanisms, the psychological basis for perceiving color is rooted in the structure of the natural visual environment.