I think you're talking about RGB (red, green, blue). It's a color system used in process printing. You have three plates (red, green, blue) A plate is something that ink runs through. I don't know if you're familiar with screen printing, but it's kind of like that. Anyway, you put certain amounts of those three colors together to make a full-color product. Ex. magazine, pamphlet, etc...Check on Wikapedia for the specifics. Another popular printing method is CMYK (cyan, magenta, yellow, black)