Complex sentence: Prints were hand-colored by a dozen or more women, often immigrants from Germany with an art background, who worked in assembly-line fashion, one color to a worker, and who were paid $6 for every 100 colored prints.
Split into simpler sentences: Prints were hand-colored by a dozen or more women, often immigrants from Germany with an art background. They worked in assembly-line fashion, one color to a worker, and who were paid $6 for every 100 colored prints.