"In the absence of a perceiver, there is no such thing as color. Colors, like other percepts, are generated by the activity of the brain, and the subjective nature of the acompanying experience is unknowable except to the person who happens to possess the brain. Indeed, there is no way to be sure that what one person calls "red" is not what another calls "green."
- from Why We See What We Do by Purves and Lotto
"Was Young really the last man who knew everything? Physics textbooks identify Thomas Young as the experimenter who first proved that light is a wave - not a stream of corpuscles as Newton proclaimed. In any book on the eye and vision, Young is the London physician who showed how the eye focuses and proposed the three-color theory of vision - confirmed only in 1959. Then again, in any book on ancient Egypt, Young is credited for his crucial detective work in deciphering the Rosetta Stone. It is hard to grasp how much he knew."
- from The Last Man Who Knew Everything by Andrew Robinson
Diagram from Traite de la Lumiere by Christiaan Huygens, 1690. For access to the complete work, see the LHL Digital Collection: Color and Optics.