Painting will be very helpful for people with post-traumatic syndrome, or those who are constantly in a stress state. The fact that such activity calms the amygdale, i.e. the area of the brain that is responsible for generating emotions. When you focus on coloring pictures, you give your brain a chance to rest and relax.
You should pick soft triquetrous pencils for a small kid. It is sufficient to have a set of six basic colors. When coloring, try pronouncing the name of each color, this helps the baby to remember them.