Colour and Light

The function of a paint, printing ink, dye or other colorant is to absorb or subtract some parts of the spectrum, and to transmit or reflect other parts. The colour is determined by which parts of the visible spectrum are reflected when absorption takes place. The process is a subtractive one. The subtractive primaries known as cyan, magenta and yellow, subtract respectively the three primary regions of the spectrum known as red, green and blue, which are the additive light primaries. Additive and subtractive primaries are complementary aspects of the visible manifestation of the electromagnetic spectrum.