The modern American coloring book, surprisingly, has its origins as far back as the late 19th century. A firm called McLaughlin Brothers produced many of the children's books of the time; in 1881 they offered The Little Folks Painting Book, which had illustrations by artist Kate Greenaway. Although crayons didn't quite exist in America at that time (Crayola wouldn't be around for another twenty years), the book encouraged the use of watercolor paints. Popular because of its novel concept and amusing illustrations, the book would continue to be reprinted for years.
Throughout the rest of the 19th century and into the first few decades of the 20th, several other publishes would produce such books for children, the design of which was simple enough for anyone to produce: clean, simple line drawings on white pages, with a colorful cover to attract browsers' interest. It was recognized early on that incorporating the popular characters of the time (at least, as many as existed in that period) increased sales. Thus, we got such items as Buster [Brown]'s Paint Book, featuring the little scamp from comic strips; in addition, parents could also purchase a Buster Brown-themed set of paints as well.
Over the next several decades the format would flourish. Such printing companies as Whitman, Saalfield, and Merrill Publishing would fight one another for dominance in the field; since this particular type of children's book was relatively cheap to produce, these publishers released dozens of titles a year. Radio and early movie personalities like Shirley Temple would give way to TV, comic book, and other mass-pop-culture characters. In fact, it is difficult to look back today at a list of 1960's or 70's films or TV shows with even the slightest passing interest to children, and not find a coloring book devoted to the subject.
These days, collecting the humble coloring book is still an unpopular endeavor: doing so has certainly lagged behind the swells of interest to other collectible items, for whatever reason. May collectors amass coloring books as simply a part of a larger pattern devoted to certain characters or themes - i.e., a collector of I Love Lucy items will certainly want to add a coloring book to his or her collection, but not one devoted to, say, Roy Rogers. There are other concerns as well: many extant coloring books from previous decades have been colored in, and thus, have lost much of their appeal for collectors who demand mint-condition items. Also, the paper used on coloring books has traditionally been even cheaper and crappier than that for other types of publications, even counting children's fare: most of them are found these days with heavily acidic, yellowing pages that are simply unappealing to most. On the plus side, however, is the fact that, since the field is not yet saturated with hardcore collectors, most items can be found rather inexpensively.
For those who might be interested, here's a rundown of ten of the most sought-after coloring books:
Mickey Mouse Pictures to Paint - Saalfield - 1931
Buster's Paint Book - Stokes Co. - 1907
Popeye Paint Book - McLaughlin - 1937
Walt Disney's Daniel Boone - Whitman - 1961
Jonny Quest Coloring Book - Whitman - 1965
Gene Autry Cowboy Paint Book - Merrill Pub. - 1940
Hopalong Cassidy Coloring Book - Abbott - 1951
Little Orphan Annie Coloring Book - McLaughlin - 1933
Dick Tracy Paint Book - Whitman - 1935
Family Affair's Color By Number - Whitman - 1969