Additive colour system starts with darkness. Light source from various wavelength is added in various proportion to produce a range of colours. Additive colour theory describes how we perceive color and how they are created. It is essentially colour created by mixing light of two or more different additive colours. The three primary additive colours are red, green and blue, otherwise referred to as RGB
Red & Green = yellow
Green & Blue = cyan
Red & Blue = magenta
Yellow, cyan and magenta are secondary additive colours. When all 3 primary colours and mixed it added together it creates white light. Computer monitors and television are most common examples of additive colours.