Technically it's a red card. Chiellini, due to his stupidity not to go for the ball, stopped a 1 on 1. There weren't other Juve players around. I'd have given a yellow here, but the ref won't get punished at all, because the rules are on his side.
Even more, if this wasn't a red card, Chiellini did deserve a red card. Yellow for the penalty and yellow for this. The ref didn't distribute the cards in a way not to provoke controversy, but even as it is, we won't really have a solid ground to object against the red card in UEFA.