CMYK and RGB color spaces

The following diagram illustrates the relationship between CMYK and RGB color spaces.

RGB color space refers to direct light composed of Red, Green and Blue colors corresponding to the basic frequencies recognized by the rods in the back of the eye. This is an additive color model since additional colors are created by adding different amounts of these three colors to black.

CMYK color space refers to indirect light, such as light reflected from paint, composed of Cyan, Magenta, Yellow and Black (Kill). These too are recognized by the RGB rods in the back of the eye, but in an inverse fashion. That is because this is a subtractive color space where new colors are created by subtracting the first three colors (and optionally black) from white.

This one diagram shows how each color model creates the other, thus forming a duality in our perception of light. Altogether, there are six hues plus white on the outside and black on the inside, totaling eight.