The original drawing was in oil crayon and ink. Refreshed rendering here. It is about the 'value' (as opposed to 'meaning') of color (colour). My colorful lecture on composition in three dimensional design, given to design students, focused on the semiotic 'value' created by particular arrangements and quality of components. They wept with joy at my delivery!

See: Kress and Van Leeuwen, 1996.