Absolutely everyone was at amfAR's Cinema Against AIDS Gala in Cannes!
Back from Versailles already, we're sad to say that Diane disappointed us with this feathered black mini dress!
Guess it's hard following up that gorge gown she wore just the day before, but she must have had so many other options!
Sienna, on the other hand, did go gold on the step-and-repeat… and absolutely killed it in her custom Ralph Lauren dress!
At least she knows what works for her!
[Image via Getty Images.]