Additive colour is based on the mixing of light of different colours. By mixing three light sources with the primary colours red, green and blue, any other colour can be created. The starting point is black (no light) and subsequently coloured light is added (hence the name “additive”) and mixed. A balanced mix of the three primary colours leads to white.
Early colour photography processes, like Autochrome Lumière, used the screen process to implement additive colour.