Equal amounts of red, green, and blue equal gray. However, the gray on the right has a color cast, it has more red and green, which creates yellow, than it has blue. In fact, much of color correction hinges on a restatement of this: “If something is supposed to be gray, it must contain equal amounts of red, green, and blue.” If it doesn’t, it has a color cast.įor instance, in this screen shot, both the left and right side are equally “bright,” they are both 50% gray.