Color attributes were first understood by 19th century physiologist Ewald Hering, who made the color charts below. His charts show how all colors arise from a combination of green-or-red, blue-or-yellow and brightness. (In his diagram, the green-neutral-red is vertical, and blue-neutral-yellow is horizontal.) The left circle shows relative mixtures of color attributes. The right circle shows what we perceive when these attributes are mixed.
The artistic term “hue” is the edges of the square (the outside of Hering’s circle); “saturation” represents where the color is placed between grey middle and the colored edge; “value,” also called “brightness” or “luminance,” is the intensity of the color and is the third attribute.
Newton set up a prism near his window, and projected a beautiful spectrum 22 feet onto the far wall. Further, to prove that the prism was not coloring the light, he refracted the light back together. Light enters the prism from the top right, and is refracted by the glass. The violet is bent more than the yellow and red, so the colors separate.
Artists were fascinated by Newton’s clear demonstration that light alone was responsible for color. His most useful idea for artists was his conceptual arrangement of colors around the circumference of a circle (right), which allowed the painters’ primaries (red, yellow, blue) to be arranged opposite their complementary colors (e.g. red opposite green), as a way of denoting that each complementary would enhance the other’s effect through optical contrast.
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