A color wheel is made up of three kinds of colors, namely, primary, secondary, and tertiary. Primary colors are those which cannot be created from other colors, such as red, yellow, and blue. Secondary colors are those which are created by mixing two primary colors, such as orange, made by mixing red and yellow; violet, made by mixing blue and red; or green, made by mixing yellow and blue. Tertiary colors are those that are created by mixing primary and secondary colors, such as yellow-orange, red-violet, blue-green, blue-violet, yellow-green, and so on.
Besides these, there are a number of other color schemes, as well, such as monochromatic, complementary, analogous, split-complementary, contrast, double contrast, and tetradic. All these color schemes are created by combining colors belonging to the three color groups from which a color wheel is made: Primary, secondary, and tertiary.