CSS Color (All Properties) Please Share On: Definition: CSS Colors are used to fill the elements in color. The color can be defined by predefined color names like red, green, blue, etc., or different property values like HEX, RGB, RGBA, HSL, and HSLA. Property Values are: 1. color name 2. HEX 3. RGB 4. RGBA 5. HSL 6. HSLA