In the movie version of the musical Jekyll and Hyde (yes, the one with David Hasselhoff), Dr. Jekyll is shown with a red light◊ (hard to tell in this picture, sorry) and Hyde is shown with a blue light shining on him◊
Romeo and Juliet gives us Romeo (red) and Benvolio (blue), Mercutio (red) and Benvolio (blue), and even Romeo (red) and Juliet (blue).
To a degree, Henry Higgins (red) and Colonel Pickering (blue) from Pygmalion and My Fair Lady.
