There are lots of tools: pencils, markers, paint crayons. Each material has its own characteristics and advantages, promoting the development of specific skills. It is recommended to start with pencils.
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.