Build your colors gradually, and layer them. Apply a light undertone, and build darker colors slowly on top. Crayons can actually be more difficult to layer with due to the high wax content. Don't confuse them with colored pencils! If you want the "look" colored pencil, just use that instead.
Psychologist Gloria Martinez Ayala tells the Huffington Post that coloring triggers and stimulates the brain areas associated with motor skills, creativity, and the senses. Coloring helps to calm the part of our brains called the amygdala, which controls our emotions and stress. Simply put? Coloring takes our minds off our problems, and as a result leaves us feeling much more relaxed, rested, and at ease. Furthermore, experts say that concentrating on a coloring book lets us mentally escape by bringing back memories of childhood, a less stressful time for many of us.