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.

Speech therapy coloring is designed to secure the child in the speech of certain sounds. They develop fine motor skills, phonemic hearing, attention, perseverance.

Nurse Coloring Pages Kids