Refers to the mixing of colors by the addition of spectral ranges. According to the trichromatic theory, the colors produced by additive color mixing are the complementary colors of the primary colors (red, green and blue). Mixing the three primary colors in equal amounts produces white light.
Super imposing several colours of light is an additive mixing process. Mixing two of the primary colours red, green and blue results in magenta, cyan or yellow. By mixing the three primary colours in equal amounts, white light is produced.