Can you imagine a reddish green? Not the muddy brown produced by mixing red and green paint, but a gloriously vivid color that looks a bit like red and a bit like green. How about a color that looks like a mix of blue and yellow, yet isn’t greenish? These exist, but are virtually impossible to see or envision — except with the help of retinal stabilization. Someday we may wear goggles to see the forbidden colors previously off limits. Via Life’s Little Mysteries:
“The observers of this unusual visual stimulus reported seeing the borders between the stripes gradually disappear, and the colors seem to flood into each other. Amazingly, the image seemed to override their eyes’ opponency mechanism, and they said they perceived colors they’d never seen before.”
Even though those colors exist, you’ve probably never seen them. Red-green and yellow-blue are the so-called “forbidden colors.” Composed of pairs of hues whose light frequencies automatically cancel each other out in the human eye, they’re supposed to be impossible to see simultaneously.