Additive Color
From George Eastman House : Notes On Photographs
The principle of additive color demonstrates that all the colors of light can be made by combining different proportions of the three primary colors of light: blue, green, and red. (These colors are the complementary colors of the primary subtractive colors: yellow, magenta, and cyan.) When the three additive primary colors are mixed equally, the result is white light. Autochrome plates and color television images depend on this principle. When white light passes through a filter colored one of the primary additive colors, the filter transmits only that color of light and absorbs the other colors. Black-and-white photographic negatives exposed through such filters are called "separation negatives." Separation negatives are required in color photographic processes such as Carbro and dye imbibition.