Coloring boos must be such as to cause a positive emotional response from the child, encourage him to draw further. For older children it is interesting to color a favorite fairy tale character, useful educational coloring.
There is another advantage of colorings for adults. Most of them are very nice and include impressive black-and-white contours that can be turned into a work of art. Imagine the feeling of satisfaction that you get when you have finished drawing and will be able to appreciate the beauty of the masterpiece created by you personally.