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
Tactical light high-efficiency white LEDs have led to a wave of brighter and more energy-efficient tactical lights. Tactical lights can be fitted with lenses to produce certain colors, Colored lights or filters provide flexibility for different purposes. Red lights are best for preserving night vision for the law enforcement officer, due to their minimal impact on the rod cells in the eye, while blue light provides high contrast for detecting blood. Light in the infrared spectrum is only visible through night vision devices, allowing the operator to see clearly while reducing the visibility to those not equipped with night vision equipment. Tactical