Love the green dressing/smoking gown with the red lining and cap ~ also the little gold slippers. The other two gents are wearing evening clothes (at left), and (at right) what looks like a typical day-to-evening frock (more casual than the dinner tails).
Aside from the clothes, I really love the ghosted-in room decor: the fireplace, candelabra, etc.
Click on the image to see more details!