The RGB color model is the unit cube subset of the 3D Cartesian co-ordinate system. A color model is a specification of a 3D color co-ordinate system and a visible subset in the co-ordinate system within which all colors in a particular color gamut lie.

In the example on the right, you can use the sliders in the lower left region of the 3D window to define a color composed from the three color vectors RED, GREEN and BLUE. The figure on the right shows the respective changing of values of the color vectors in realtime.