In figuring out color management, I read all about how our eyes work and that's when I learned that we could see only three colors of light—red, green, and blue. Every-thing we see is a combination of those colors. That's right, when you look at a rainbow, all your eyes see are red, green, and blue (Figures 7.1 and 7.2). When we see all three of those colors in a balanced amount (equal amounts of red, green, and blue), we see white light. The more light there is, the brighter it is; the less light there is, the darker it is. We often call a low level of white light gray, so that's what I'll call a balanced amount of red, green, and blue. When they aren't balanced, we see color. Photoshop works the same way.