Yes, I'd leave them black or sepia, but keep the omnidirectional light, to simulate a projector, as Nanner said.
As for Nosferatu, I'd try and go with the original theatrical cards. I mean, DVD releases shouldn't mean anything for such a movie. ;) Everything beyond the theatrical is just whatever company is releasing it felt like doing, not the director of the movie. To that end, did the theatrical cards have color in them, or all black or what?