Try to use a themed coloring. For example, a series of coloring books about animals, buildings or machines give children an idea of the objects of the world. Coloring of fairy tales or cartoon characters, are good because they allow the child to "talk" with their favorite characters and express their attitude towards them through colors.
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.