The Splash photographers believe her dress to be this lovely coral color.
While Getty Images' images are a bit more peach. I suspect the truth lies somewhere in between -- and, regardless, part of the magic of Cate Blanchett is that she looks good in EITHER shade. She's like Two Face, if both halves of Two Face were hot.
I enjoy the expression of the woman in the background here. She's clearly thinking, "pockets lined in a contrasting color. I like it."