The Divorce of Lady X with Laurence Olivier and Merle Oberon.  Olivier is a divorce lawyer who takes a room in a hotel to wait out a particularly bad London fog.  Oberon cajoles him into sharing his suite with her (in separate rooms) because there are no vacancies.  Olivier gains a new client the following day who wants to divorce his wife because he is convinced she spent the night in a hotel with a man, and Olivier is convinced that Oberon is the wife in question, whom he has decided he loves.

This is my third color movie.  Olivier is okay but I think comedy is not his metier.  Merle Oberon is cute and precocious but thoughtlessly cruel as she misleads Olivier for her own idle amusement.