While such heuristics generally work fine for limited color mixing tasks needed in an area like interior decorating, actually every part of the answer above is false. There is nothing special or "primary" about red, yellow, and blue (i.e. that can't be accomplished with any number of other color combinations. You can make red, yellow, and blue from other colors, and you cannot make every other color out of red, yellow and blue. The only "colors" from which all other colors can be mixed are not only entirely arbitrary, but are not visible, and hence not "colors" at all -- for details see http://www.peterga.com/notes/science/color-questions.htm#primary