Pygmalion's Art Tutorials: About Color Schemes: Tetradic (Double Complementary)
This color scheme is the richest of all because it uses four colors arranged into two complementary color pairs. Like Triadic, is referenced by the number Three, this color scheme is named Tetradic after the Greek word for the number Four, Tetra, indicating its four colors.
While it is a very rich color scheme and creates a goodly amount of dynamic tension, it is for this reason that it is also hard to harmonize. If all four colors are used equally throughout the piece, the scheme can look unbalanced. One way to avoid this is to choose one dominant color and/or subdue the colors.
Find below, a screen shot from the Kuler web site to see an example of a tetradic color scheme.
The six color schemes are: Monochromatic, Analogous, Complementary, Split Complementary, Triadic and Tetradic. Make sure you review all of them to get a complete understanding of color schemes.

