Adding a small (or large) amount of common color to all the colors, creates color harmony in your art. For example, you could add orange to all the colors in your painting. You can achieve this by mixing the orange into all of the colors on your palette, or you can do it simply, with an overall glaze of orange. All the colors would be sharing a little of that orange.
This also can be achieved by taking a small amount of all the colors you are using, mixing them into one muddy color, and then adding this new color to all the colors when making them. This muddy color was created from all the colors, and even a small amount of it mixed into each color will make them relate and harmonize. All the colors actually have a small amount of each other’s color within them.