Red, blue and yellow are the primary colors and are the base of every other color. They cannot be recreated by mixing other colors together. Secondary colors result when two primary colors are mixed together; they include orange, green and purple.
Tertiary colors are created when a primary color is mixed with a secondary color. Examples of tertiary colors are blue-green, red-orange and yellow-green. Continuing to mix colors together provides an endless mix of possible hues.
White and black are not technically colors but they can be used to create lighter or darker shades of other colors. For example, combining white and red makes pink, and blending black with orange makes brown.