The 9 is, as far as I’m concerned, probably the closest to that which would symbolize death, and that is it’s a black, white and yellow painting. Well, many of my—not many, but some of my new paintings have used the colors of black and yellow and black and yellow comes directly from traffic signs, and though not all traffic signs, of course, are expressive of danger, and so forth, still black and yellow to me infers danger.
— Robert Indiana
Arthur C. Carr, “The Reminiscences of Robert Indiana,” New York, November 1965, Arthur C. Carr papers; Rare Book and Manuscript Library, Columbia University Library, p. 95.