Gage covers topics as diverse as the optical mixing techniques implicit in mosaic; medieval color-symbolism; the equipment of the manuscript illuminator's workshop, the color languages and color practices of Latin America at the time of the Spanish Conquest; the earliest history of the prism; and the color ideas of Goethe and Runge, Blake and Turner, Seurat and Matisse.

From the perspective of the history of science, Gage considers the bearing of Newton's optical discoveries on painting, the chemist Chevreul's contact with painters and the growing interest of experimental psychologists in the topic of color in the late nineteenth century, particularly in relation to synaesthesia. He includes an invaluable overview of the twentieth-century literature that bears on the historical interpretation of color in art. Gage's explorations further extend the concepts he addressed in his prize-winning book Color and Culture.