“The most noticeable difference between graphics of the period between the two world wars and today is the absence of full colour in the former, although colour photography was pioneered in Russia well before the First World War. Few of the works in this book are in more than three colours; many are printed only in black and red. For a full-colour effect, designers were ingenious in overprinting two or three colours, and they exploited a traditional printing technique that spread ink of varying colours across the printing press rollers to give a rainbow effect.”

—Richard Hollis, from Art + Technology = Design, an essay in the wonderful (if you like this kind of thing) Avant-Garde Graphics: 1918?1934, 2004.