Subtractive colour, also know as CMY (Cyan, Magenta, Yellow) is a subtractive colour system which involves reflections or absorption of wavelengths of colour
and reflective light on an object such as paper that reflects back wavelengths of white light that illuminates colorants such as pigments, dyes or inks to produce & reflect other colours to the viewers eye. The viewer (or detector) can be the human eye, film in a camera or a light-sensing instrument.
If an object reflects all the white light back to the viewer, it appears white. If an object absorbs (subtracts) all the light illuminating it, no light is reflected back to the viewer and it appears black. When combined in equal amounts, pure subtractive primary colors produce the appearance of black. It is the subtractive process that allows everyday objects around us to show color.
The printing process uses cyan, magenta and yellow (CMY) inks and a fourth ink, black which symbol is ‘K’. Overprinting one transparent printing ink with another produces the subtractive secondary colors, red, green, blue. Process printing inks are transparent. It is the paper that reflects unabsorbed light back to the viewer.