When you use a color model to define colors, you manually adjust its components, such as the amount of pure red or the amount of saturation.
You can choose from three color models: CMYK, RGB, and HLS.
Use the CMYK model to create color separations for four-color process printing. Colors are created by combining cyan, magenta, yellow, and black (CMYK) inks. In color separation, each color component is printed on a separate plate, in a different concentration, depending on the desired color.
Use the RGB model to create colors that are viewed on a monitor (for example, for online documentation). Colors are created by combining red, green, and blue (RGB) light.
Use the HLS model if you are familiar with color wheels. This model is most like the one artists use to mix colors and is often used in software color pickers. Colors are created by adjusting hue, lightness, and saturation (HLS). Hue controls the amount of red, green, yellow, blue, and so on. Lightness controls the lightness or darkness of a color. Saturation controls the amount of gray in the color.