Commentary colors contrast and tend to produce gray tones or variations of the original colors that are darker. There are many tonal variations of colors in nature and mixing complementary colors can produce these different tonal ranges. Here is another experiment to try out for yourself. Paint a tree in nature or from a picture. As you begin to work on the green leaves, you will soon begin to notice that there are various differences in the tone of the green.
Some greens are lighter and some darker and some purplish.
Mixing the original green with complementary and similar colors creates these variations. Variations of green, for example, can be made with a mixture of red. A note on this aspect is important there. Instead of using ordinary black for your shadows, you should mix the colors that you are using with their complementary colors to create a deep black. For example, by mixing the green with the reds you will eventually create a deep black which will have the advantage of having elements of both the original colors, and so create a shadow area which is much more realistic.