There is no artist, who would buy their children coloring books or taught to paint pictures. What does this mean? Coloring is a kind of framework, hindering the development of the imagination. They contribute to the formation of habits of the finished drawing, in which a flight of fantasy and free creativity is almost impossible.
Buying coloring for children, look for task-coloring, in which you need something painted in a specific color, something to finish, something to paste, draw a line through the maze, etc.