Almost all visible colors can be obtained by the additive color mixing of three colors that are in widely spaced regions of the visible spectrum. If the three colors of light can be mixed to produce white, they are called primary colors and the standard additive primary colors are red, green and blue.
Two colors that produce white when added together are called complementary. The color complementary to a primary color is called a secondary color. The complementary or secondary colors for red, green and blue are cyan, magenta and yellow respectively. These three colors are often referred to as the subtractive primary colors. When the three are combined in subtractive color mixing, they produce black.
Williamson & Cummins