“Find the papers about colors considered in the sense of coloring light sources and not differentiations within a uniform light (sunlight, artificial light, etc.)

Come back to:

Supposing several colors – light-sources – (of that order) expose at the same time, the optical relationship of these different coloring sources is no longer of the same order as a comparison of a red spot with a blue spot in sunlight. There is a certain inopticity, a certain cold consideration, these colorings affecting only imaginary eyes in this exposure. (The colors about which one speaks. A little like the passage of a present participle to a past one.”

“I mean the difference between speaking about red and looking at red. [M.D., 1965.]”

(Duchamp, note in Á l’Infinitif (The White Box) (published 1967), trans. Cleve Gray.)