Schäffer's principal colors were red, yellow, blue, white, black, brown, and green, and he includess "members"—the pure colors —of each group. The heraldic imagery of the presentation suggests an extra significance for red, yellow and blue, in the size and placement on the page of those shields. Source: Farbenmuster der sieben einfachen und natürlichen Hauptfarben. From Jacob Christian Schäffer, Entwurf einer allgemeinen Farbenverein . . . (Regensburg, 1769), plate I.

From The creation of color in eighteenth-century Europe by Sarah Lowengard