On Vision and Colors tried to demonstrate physiologically that color is "specially modified activity of the retina." The initial basis for Schopenhauer's color theory comes from Goethe's chapter on physiological colors, which discusses three principal pairs of contrasting colors: red/green, orange/blue, and yellow/violet. This is in contrast to the customary emphasis on Newton's seven colors of the Newtonian spectrum. In accordance with Aristotle, Schopenhauer considered that colors arise by the mixture of shadowy, cloudy darkness with light. With white and black at each extreme of the scale, colors are arranged in a series according to the mathematical ratio between the proportions of light and
School colors follows the rule of tincture from heraldry, but exceptions to this rule are known. Common primary colors include orange, purple, blue, red, and green. These colors are either paired with a color representing a metal (often black, brown, gray (or silver), white, or gold), or occasionally each other, such as orange/blue, red/green, or blue/yellow. Pairing two metals, such as black/white, silver/gold, and especially black/gold, is also a common practice. Finally, some American schools, in a display of patriotism, adopt the national colors of red, white, or blue. In an effort to further establish identity and promote a standard, many institutions