CMY colour cube coordinates :

One may understand the subtractive nature of the CMY model in the following sense. When white light falls on a white page, virtually all of the light is reflected and so the page appears white. If white light strikes a region of the page that has been printed with cyan ink however, the ink absorbs the red portion of the spectrum and just the green and blue portions are reflected. This mixture of reflected light seems as the cyan hue.

In terms of the CMY colour cube coordinates, one may think of the origin, (0, 0, 0), as three colour filters with a tint so faint that they seems as clear glass. In terms of absorbing inks, the origin corresponds to pastel shades of cyan, magenta, and yellow as faint as to seem white. As one moves up along with the M axes from (0, 0, 0) towards (0, 1, 0), it corresponds to turning the density of a tinted filter up towards the maximum possible. In terms of inks, this motion up the M axis corresponds to moving from a pale pastel towards a pure magenta. If one uses all of three filters in sequence (or a mixture of C, M, and Y inks), eventually all light is absorbed as one gets to pure colours of filters or inks. It is point (1, 1, 1).