Butterflies in general? I think he would put them in the same category as flowers. Neither butterflies nor flowers are gentlemen (or valets) and therefore may be as colorful as they like. He can appreciate the scent of flowers and, in fact, he's happy to put one in Bertie's buttonhole, as is proper. To actually wear such colors as a main theme, though? Most improper, sir. Most improper. I could not advise it.