Extra-Spectral Color

An extra-spectral color is any color that cannot be excited by a single wavelength of light. They are not on the Spectral Locus and therefore are not Spectral Colors. “All the colors of the rainbow” are Spectral Colors, but every other color is an Extra-Spectral Color, including purples (see Line of Purples), desaturated colors and neutral colors (like white).

People try to discredit purple as not being a real color because it is not a Spectral Color, but 99% of all colors are Extra-Spectral Colors