Subtractive Colour System Subtractive colour filtering is essentially the reverse of the additive colour system. Instead adding light from several primaries, we start with white light (i.e. a uniform distribution of wavelengths along the entire visible spectrum) and selective filter out portions of the spectrum. This principle is used in the printing industry where of course white (or almost white) light shines onto paper and is filtered in the reflection process by the printing inks. The usual primaries for subtractive filtering are magenta, cyan and yellow. A Magenta filter for example eliminates all the ‘green’ light and let’s only the red and blue component through (this is the equivalent of additive colouring with blue and red light being emitted and no green light added). We can ‘translate’ between the two systems by combining different filter. Stacking a magenta and cyan filter will create blue light (Magenta filters the green component, cyan filters the red component so only blue light is left).