Dear Color Challenged,
In addition to the marvelous response given by Katya, may I add my two cents?
I work at the Bookstore of a different university, and the colors the professors wear have an additional connotation. Not only are they wearing colors from their specific department, they are also wearing the colors of the school they graduated from. If you happen to have a professor that graduated from the U of U, for example, werf will probably be wearing red somewhere with the cap/gown/tassel/hood combo to let you know that.