The younger the child, the larger and easier the drawing is. The outlines are indicated by a thick line from 2 to 4 mm, so that for the child it is easier to stay within the contours.
Coloring also takes us back to a time when everything was easier. You agree that such activity would seem more suitable for kids than for adults. In fact, painting is associated by most people with the period when they did not have much to do, and carelessness was more than enough. In order to take a little dip into childhood and clear the emotional background, coloring is an ideal option. It seems to take us out of the current stress state and allows forgetting about everything for a few hours.