Our school had them in the 50s, which is when that photo was taken, judging by the girl's hair and clothing. Our fifth-grade teacher had our class do the school newspaper, and she provided three different colors of ink forms—fuschia, turquoise, and the standard purple. One of our clever girls was able to envision three-color printing and figured out how to draw differents parts of the same illustration on each of the different color forms, then run the paper through three times to get the whole picture to fill in.
She later became a production artist for a big printing house, IIRC, which was unusual for suburban girls from that era when they were herded into being only housewives, teachers, secretaries or nurses. Her drawings were just stick figures and the school house, etc.; but "color separation" technology for commercial printing is still in use today (but now done digitally).
I looked online and found these images of professional color separations:
