"Made in honor of such friends as Marsden Hartley, Georgia O’Keeffe, Wallace Stevens, and Eugene O’Neill, these paintings, watercolors, and drawings used objects and wordplay to convey the life, rather than the likeness, of the sitters." (http://artgallery.yale.edu/publication/charles-demuth-poster-portraits-1923-1929)
O’Keeffe’s portrait practically shouts the letters of her last name, which people were always misspelling. Here Demuth is telling her (and us) that he knows her well enough to remember how many Es and Fs to include.... These witty details personalize the images, but only make sense if you know a bit about Demuth and his friends, which is perhaps why critics were slow to appreciate the cleverness of the poster portraits. (https://www.khanacademy.org/humanities/art-1010/art-between-wars/american-art-wwii/a/charles-demuth-i-saw-the-figure-5-in-gold). One site (atheneum) says the poster was done with poster paint; another (kahanacademy) says oil paint. Who knows? Who cares?