There's a very good podcast about the blu-ray release interviewing colourist Marc Wielage who worked for ILM on the 2004 release.http://www.fxguide.com/thevfxshow/th...u-ray-release/
I transcribed some outstanding excerpts:
Marc Wielage: Back in 2004 I was sort of hired as a freelance colorist by Industrial Light and Magic who had set up a temporary color correction room up there is San Rafel at their old building up there on Kerner Boulevard and they had set up a Pogol color correction suite which is now considered very outdated, and we did all the color correction basically out of a closet. Entirely the opposite of what you would consider a THX color correction room. ILM wanted to handle it there rather than going to a conventional color correction suite in London or New York or Hollywood because they wanted to be very hands on and control every aspect of the transfer with great secrecy and security.
Marc Wielage: The jury is still kind of out on that. I was able to watch Star Wars, that is to say: Episode IV completely from start to finish last night, and I am torn on whether this is an entirely new scan and new transfer, or the old scan and a new transfer, or bits and pieces of my transfer with some new bits, or what it is. I think it’s kind of a hodge-podge. I did see some certain scenes, particularly the opening shot in the white corridor where the Storm Troopers are running down the hallway and shooting blasters back and forth and I caught a few white wall color matching issues which are the kind of thing I would never let go by. They’d be a little bit blue tinted in one shot, a little bit warmish in another shot, and a little bit neutral in a third shot and I thought I don’t remember it looking quite that inconsistent. So and yet other scenes look exactly like what I did. It’s very possible that a new transfer was done, or at least a new color correction was done, and that they precisely matched it to what was done back in 2004 by myself and Rich Garabaldi who was the other person working on the show. Its possible that they diverged a little bit because you know over time peoples minds do change about how they want color.
Marc Wielage: Yes, what I was told by a very high ranking Fox post production executive in the nineteen nineties was that the original cut camera negative of Star Wars had been extensively damaged in Japan at some point during the nineteen eighties and I think nobody had been aware of it until they opened up the cans around ninety-five or ninety-six and saw that there were massive scratches on the emulsion side of the film. The exact words of the executive to me was it looked like someone held a fork up to all seven rolls of film and just scratched them right down the centre, which sounds horrible. In addition to that there was a tremendous amount of negative fading and color shifting and density flutter and things like that going on.