I'm sure Mark Hamill was not bright orange, when they filmed the sunset shot, but I'm quite sure the sun illuminating him was. I'm also quite sure he didn't have a sickly greyish skin during the shoot either. I'd say his skin probably looked something like it does in the pictures on the right:

People got so obsessed with the sunset shot, that no-one even commented on these. You can't honestly tell me that these are oversaturated. Look, even Fredie's skin is more orange than Luke's in those pics.