Primary Colors: Red, yellow and blue
Primary colors are three colors that can not be mixed or formed by any combination of other colors. All other colors are derived from these 3 hues.
Secondary Colors: Green, orange and purple
These are the colors formed by mixing the primary colors.
Tertiary Colors:Yellow-orange, red-orange, red-purple, blue-purple, blue-green & yellow-green
These are the colors formed by mixing a primary and a secondary color.
Colors which appear on opposite sides of the color wheel are called Complimentary Colors. Contrary to belief, these colors are called complementary because when mixed together produce a neutral color (grey,white or black), and not because they necessarily look good together. Usually when paired, colors like red and green, blue and orange, and purple and yellow create a harsh contrast which may get you noticed for all the wrong reasons.
However, contrast can be fun when done the right way. And although they may not be 'complementary' in color wheel standards, there are colors that compliment each other in a fresh new, color harmonizing sort of way: