This gif is comprised of the pages of a lithograph color separation proof book from the Louis Prang papers (Prang was one of the premier lithographers in Boston in the 19th century). This particular lithographic print is made out of 18 different color plates - the pages on the left show the individual plates and the pages on the right show how the print looks after each color is added. With apologies to houghtonlib for biting their style, but this was an excellent idea!
For more on the process of chromolithography, and this proof book in particular, see this blog post.
Color separation proof book, circa 1890. Louis Prang papers, Archives of American Art, Smithsonian Institution.