Primary Colors are basic and cannot be mixed from other elements. They are to color what prime numbers are to mathematics. One can mix two primaries to get a Secondary Color. You will notice that each Secondary Color on the Color Wheel is bounded by two primaries. These are the components that one would mix to get that Secondary Color.
Secondary colors are the hues between the primary hues on the color wheel.
To get orange, you mix equal parts of red and yellow. To get Violet, you mix equal parts of red and blue. To get green, you mix equal parts of blue and yellow. Complimentary colors are colors that are across from each other on the color wheel. Violet and yellow are complimentary, Blue and orange are complimentary, and red and green are complimentary.