Primary Colors Red, yellow and blue are single colors, while all other colors are a mix of colors. Undertones are found in all colors except primary colors. An undertone in a hue hints at a second subtle color or the color beneath the color. Olive is a good example of a green with yellow undertones. Pairing olive with yellow will emphasize the olive to a greater degree than if you decide to down play the yellow undertone by using its complement, which is red.
