It is believed that the company The McLoughlin Brothers (en.wikipedia.org/wiki/McLoughlin_Brothers) invented the coloring books. They published a book called The Little Folks' Painting Book in collaboration with Kate Greenaway in 1880.

Children can start coloring the picture at 1.5 years. For this age there are special coloring books that the child will paint without using brushes or pencils, but his own hands. You can find finger paint palettes on the market. Such colorings have got very simple and clear pictures to your child: ball, pinwheel, pear, apple ...

Olympic Color Pages