I wouldn't mind seeing blood on the Rancor in that shot, but I dunno about it being green. Anything to make ROTJ a bit more mature. And, really, how could it not bleed in that situation?

--edit--

And I'd also like to throw in my two cents and say that I agree with what many have said here - the Rancor scene was perhaps the only thing about the 2004 editions that I prefer over any other version, and beyond color correction, I don't think anything new needs to be done to the scene (minus the blood in the shot above).