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 …

…different levels; tri-chromatic through the processing that occurs at the retina, and opponent process theory to explain after images. The eye is a delicate tool that gives us the ability to see the world as a beautiful place. Explaining our vision of color has been troublesome, and is still difficult. However, it appears that working together both the opponent process theory and the tri-chromatic theory gives us the reasoning behind our ability to see color.