Master of Serumido, Deucalion and Pyrrha, c.1505-6

This is a grisaille painting on the back of Raphael's portrait of Maddalena Doni. How might this monochromatic grisaille signify the essence, meaning, or relevance of the colored image it accompanies? Is the relationship between grisaille and colored image like the relationship between motto and image in emblems and imprese?

Done