HSB

The HSB color model defines color as hue, saturation, and brightness. This is the most natural way to think about color as it allows the user to choose a hue representing the colors of the rainbow in their most color form. From there you can adjust the saturation of the color. For instance, removing all saturation would result in a greyscale color. Lastly, the brightness of the color can be set as well to make the resulting color from bright to black.