Many systems were devised to teach people about the various properties and harmonies of color. Jorgensen’s color cards provide a set of 90 color combinations resulting from a systematic mixing of what he considers 18 fundamental colors. A mask with 10 cut-out rectangles can be placed over the continuously mixed tones to get a stepped up effect of 10 different colors.
Production of color theory books was complicated by the difficulty of printing accurate colors. Many color books and charts included the colors as glued-in pigmented chips. Jorgensen boasts that his card system contains pigments applied by the artist himself in his studio.