Around 40 years ago I studied the Element “color” in regard to the Principle of Design “harmony”. One I studied was Ed Whitney’s book, Complete Guide To Watercolor Painting. In it he talks about 5 color harmonies: Monocromatic Harmony, Analogous Harmony, Complementary Harmony, Split Complementary, and Triadic Harmony. I took a workshop years ago from Margaret Ellerman and she listed: Analogous, Moncromatic, Complementary, Triad, Split, Double, and Sextad. All these harmonies have to do with what part of the color wheel we might use. For example: Analogous is where 3 to 4 colors located adjacent to each other on the color wheel are used. The reason for pre-deciding what part of the color wheel we will use keeps us from using everything in the color wheel -which may in some cases be OK. I personally have probably used the Triad Harmony most i.e. making a triangle in the color wheel and limiting myself to using only those colors in the triangle. However, I might use one color out of that triangle in the focal point with a light repeat of that color in a couple of other places. If that is too much for us to take in then I have been told in the past just Color Me Brown and Blue. You might like looking at another person’s description of Color Harmony.