Ferran Delgado : "Making of the cover. Drawing in two separate Craftint boards, one for the background using Cyan ink and the second one for the black plate. The red lines mark the limit of the green effect, and they need to be removed after used.
EDITED: Bear in mind that what you see in the original art is distorted. Craftint sheets were special because they reacted to special chemicals. When used with a brush, the area « painted » showed lines in black, while the liquid was transparent. But with time, the chemical became brownish giving a different look not intended by Janson."