Sometimes it takes a lot of time and resources to demonstrate something, and sometimes only a few props are enough. Physicsfun shared a short video which demonstrates exactly how CMYK works using only four acrylic coasters and a famous painting.
Cyan, magenta, yellow, and black (key) are the elements of the subtractive color model used in most color printing. It works by partially or entirely masking colors on a white background, and the ink reduces the light that would otherwise be reflected. Thus, CMYK model is called subtractive because inks “subtract” brightness from white.