RGB colour model works in practice by asking three questions of any colour: how red it is (R), how green it is (G), and how blue it is (B).
The RGB model is popular because it can easily be used to produce a comprehensive palette of 1530 vivid hues simply by adjusting the intensity of the three primaries.
When the saturation or brightness of a hue needs to be adjusted it is sometimes easier to switch to the HSB colour model.