Tetrad Color Wheel

Some things I've learned about painting with a "tetrad" color group:
* Choose from the color wheel what your dominant color will be
* Next, choose a "sister" color either 2 to the left or right of the dominant color, or 3 to the left or right of the dominant color.
* Now, the remaining 2 colors are chosen for you by making a straight line across the inside of the color wheel as in this diagram.
* The tetrad consists of 4 colors, not just any random colors; they are in harmony.
* Instead of a square or rectangle you could think of it in terms of an "X" - across from each of your chosen colors, is it's complement. Striking grays can be created by mixing complements, or used in it's pure color make the painting sing.