Today there is a large set of coloring books. You can find coloring-cursive books, books outliners, for boys (all sorts of appliances, machines, robots, etc.), for girls (fairy-tale characters, dolls, funny funny little animals). There's even a wallpaper coloring books that opens a wide field to have enough space for young artist.
When painting figures (for example, from 1 to 10) it develops a color perception, fine motor skills, attention, diligence and accuracy, mathematical ability. Such tasks are connected to the process logic of painting, allow to fix the basic math skills or letters.