A physical impossibility

White light contains a mixture of all wavelengths in the visible spectrum. It is the dirtiest, muddiest color possible. But the visual system does not model it in that way. Instead, the visual system encodes the information of high brightness and low color. That is the brain’s model of white light— a high value of brightness and a low value of color, a purity of luminance— a physical impossibility.

Consciousness and the Social Brain by Michael Graziano

Image from here