Jacob Christoph Le Blon, Head of a woman, 1725.
According to Le Blon, three-color printing could reproduce "all the degrees of lights and shades" found in the flesh tones. Lifelike modeling of skin tones was considered the most difficult aspect of reproduction.
Source: From Coloritto, or the Harmony of Coloring in Painting . . . (London, n.d. ), plate 3, after page 27.
Credit: Courtesy V&A Images / Victoria and Albert Museum. CT67605.