This is a paper on color vision, highlighting the tri-chromatic and opponent process theories.

Every morning and every night, all across the world, people gaze up into the sky to catch a glimpse of the sun in motion. In today's fast-paced society, people rarely have time for breakfast. What makes a sunset such an attraction? An every day occurrence, sure, but nevertheless breath-taking, sunrises and sunsets give off the most brilliant colors, like you're seeing it for the first time, every time. This may sound like a cheap hallmark card, but the fact is that color makes this world a beautiful place. The colors most people see every day are taken for granted, and most people could not understand living in a world without them. However, some unfortunate people do not have the ability to see color. Because it is a psychological interpretation and not a physical characteristic of light itself, color blindness exists. What is it that gives most people the ability to see color?

Since no theory is infinitely precise, each is accurate to a certain respect and degree.

Hermann von Helmholtz

Deutsch: Statue von Helmholtz vor der Humboldt-Uni...

“日落西山雲海觀 日落西山云海观 Sun...

There are two theories that explain color vision which I will talk about in this paper. One is the tri-chromatic theory. This theory states that the human eye has three types of receptors with various sensitivities to different light wavelengths in the visible spectrum. For example, lights with the longest wavelengths appear red, and those with the shortest wavelengths appear violet. "Wavelength is most closely related to hue, amplitude to brightness, and purity to saturation (Weiten 140)." This notion of color perception was first stated by Thomas Young and later adapted by Hermann von Helmholtz in 1852. Helmholtz believed that the eye contains receptors that are sensitive to the three main wavelengths associated with the colors red, blue, and green. According to this theory, three colors are all the eye needs to see...