Coloring helps the child to learn how to control the scale of his hand. Please note that when the baby is just started to draw he does not monitor the boundaries of the sheet, and the picture is not painted on the outlines, and even beyond.
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.