Over on the steve hoffman forum there's an ongoing thread for the blu release:

http://www.stevehoffman.tv/forums/showthread.php?t=238224

One poster actually worked on the 04 transfer and has given some insight about the coloring etc.:

George only came in during the mornings on Tuesdays and Thursdays and would approve new shots, review old shots, and revise stuff as needed. The rest of the time, I just used my best judgement to get the shots in the ballpark. But everything you see is 100% what he wanted. The 2004 version was the first (and so far, the only) time that the home video transfers were exactly what the director intended you to see.

Wayneklein earlier is correct: they pretty much have 2K scans of everything, even some trims and unused scenes, so master copies exist in a sense. But the original Kodak 5247 camera negatives are extremely beat-up and turning magenta (fading yellow & cyan layers), and it's not going to last much longer.

The problem is, the restoration was only done on the new version, not the unused shots from the original "classic" version. The expense of cleaning all those up and then conforming the 1977 version would be pretty astronomical.

Originally Posted by captainsolo

Vidiot, do you think that the final 04 version reflected the original film (instead of George's wishes) in any way in regards to color? Comparing to photos of prints, cells, and even over saturating the 06 bonus release it doesn't match.

Yeah, I was in a room that was just down the hall from the big screening room in Building C at the old Kerner Blvd. facility. We occasionally would adjourn and go down there and compare what I was doing to a print. Now, I think these were the 1997 prints, but those were timed and supervised by George at the lab. Again, it's all a subjective call; these are not absolutes in terms of right or wrong. Lucas is very, very astute when it comes to photographic issues; he actually lit part of Star Wars himself (like the trash compactor scene), so he knows color timing backwards, forwards and sideways.

Originally Posted by Ziggysane

The original trilogy all appear to skew towards a blue/cool tint (forgive my lay assessment), despite being worked on by different colorists.

They lean towards what the director wanted. I did most of Jedi, all of New Hope, along with Rich Garibaldi doing some of the final touches; Natasha Leonett and Rich did Empire. But we all worked in the same room and could see each other's work as still frames. All three of us are credited on the bonus disc.

We'll traditionally lean the whites towards blue to give them a "whiter" look, and I did that in the opening shots of New Hope because of the corridors and stormtroopers. On a monitor set to 6500-degree whites, it's going to look fine; on a consumer monitor with very bluish whites, it'll be too blue. I watched the DVDs (and seen the 2K digital projection), and they look fine to me.