Theory of Colors

When the eye sees a colour it is immediately excited and it is its nature, spontaneously and of necessity, at once to produce another, which with the original colour, comprehends the whole chromatic scale. — Goethe

Philosophers have come to understand the distinction between the optical spectrum, as observed by Newton, and the phenomenon of human colour perception as presented by Goethe.

Yellow is a light which has been dampened by darkness; Blue is a darkness weakened by light.
—Goethe