Wikipedia
Chromoxylography was a colour woodblock printing process, popular from the mid-19th to the early-20th century, commonly used to produce illustrations in children's books, serial pulp magazines, and cover art for yellow-back and penny dreadfuls. In the 19th century the art of relief engraving and chromoxylography was perfected by engravers and printers, most notably in England by Victorian engraver and printer Edmund Evans. A wide range of hues and tones were produced by the color mixing of the chromoxylography process—a technique that was complicated, requiring intricate engraving and printing for good results. Less expensive products, such as covers for pulp magazines, were coloured with as few colours as possible, often only two or three, whereas more intricate and expensive books and reproductions of paintings used as many as a dozen or more colors. For each colour a separate woodblock had to be carved.