1. - WHAT IS COLOR?
Color is the aspect of things that is caused by differing qualities of light being reflected or emitted by them, as received by the human eye and processed by the human brain. It is a function of light and biology, not an exact science, no two people can see it exactly the same.
The human eye and brain together translate light into color. Light receptors within the eye transmit messages to the brain, which produces the familiar sensations of color. Newton observed that color is not inherent in objects. Rather, the surface of an object reflects some colors and absorbs all the others. We perceive only the reflected colors. Thus, red is not "in" an apple. The surface of the apple is reflecting the wavelengths we see as red and absorbing all the rest. An object appears white when it reflects all wavelengths and black when it absorbs them all.
"Colors are the deeds of light, its deeds and sufferings."
(Johann Wolfgang von Goethe)