The human eye (more accurately, the human brain) creates patterns. Add the evolution of the eye to see the full visible spectrum as white, and you end up with a piece of technology that expects to see all three primary colors in its field of vision at all times. A look on stage composed of only two of those colors leads the eye to turn the least saturated into that missing third color. Using only red and blue, the eye desperately searches for green, and will take liberties to turn non-green light green if it has to. The shadow color of a light is perceived to be its complement. Consider a sodium vapor (orange) streetlight. The shadow has a faint tinge of blue or cyan, depending on the exact color of the lamp. Missing color syndrome is the perceptual phenomenon that occurs when one or more lights with more saturated color plays against a less saturated or clear light. The less saturated light takes on the appearance of the shadow color of the more dominant light. Clear, intended as white, playing against L106, appears cyan. A pale tint of cyan, but cyan nonetheless. Using a pale pink (more precisely a minus green) like G108 or G109, the clear looks white again. This minus green is not a perfect white, but it is white in relationship to the red. It is a reference white.
—Lucas Benjaminh Krech, from “Focus on Fundamentals,” PLSN, May 2011
