In the process of painting you focus your attention on a subject that is at your fingertips. If you do it with enough concentration, it will ignore the extraneous noise, unpleasant thoughts and worries. This is a very useful skill that will be useful in situations where you need to briefly forget about your physical or emotional pain.
In 1940 some movie stars became so popular among the coloring books industry. Among them Judy Garland, Betty Grable and Margaret O'Brien.