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.
Coloring appeared in the United States as part of the "democratization of art", inspired by a series of lectures by British artist Joshua Reynolds and the works of the Swiss educator Johann Heinrich Pestalozzi together with his student Friedrich Friedrick Frobel.