Getting back to this excellent--and unique--(thanks PP) topic:
Mark wisely observed that the ol' black shirt/white tie gangster cliche was put to bed in the Trilogy. But FFC resurrected it, probably deliberately, in II:
In the New Year's Eve nightclub scene, Fredo shows up in classic gangster threads: white Panama, white suit, black shirt, white tie. Seems like he's preparing for an audition for "Scarface" (too bad Al beat you to it, John). I think FFC dressed him that way because Michael had asked him to show the visiting politicians "a good time," and Fredo replied, "My specialty, right?" So, put in his usual sleazy position, the ol' bordello and Mickey Mouse nightclub operator dressed the part.
BTW: As the quality of Trilogy home videos improved, I noticed an amusing detail. In the earlies VHS tapes, I thought Fredo had a black hankerchief in his breast pocket. Now I see that it's a bunch of cigars.