There are many ways to tackle finding the original colors. Various members have various theories. One that held favor for quite some time and still does for many are to use the Technicolor IB prints as the example of what Star Wars looked like in 1977. An infrequently screened Technicolor IB print does not fade, however many have noted a green tint to them that seems to stem from bad quality control during the last days of Technicolor. DrDre is working on an automated color correction algorithm that is producing outstanding results. My take has been to gather on set and publicity photos from as many sources as possible as well as photos of the models and costumes and then use these to manually color correct the films. I favor using the 2006 GOUT DVD’s (once they are corrected to the sources) because he HD sources are a mess, especially for the original movie.
Unfortunately the only accurate source in existence isn’t in public hands and hasn’t been worked on to my knowledge. Back in 1977, they made a 3 color separation of the original negative with the original color timing. In the 1990’s they found that the elements had some shrinkage, but being 3 separate films, they had not done so evenly so they had become useless for duplicating the original negative using photographic methods. Since then, so many movies have had that problem that they have tackled it digitally and can easily realign the elements to create a digital master. There is no word that they have done or are planning to do that. Nor is there any word whether they kept the 3 color separation (though with GL’s packrat tendencies it seems likely that they did) after they found the shrinkage problem. I haven’t heard that there is anything similar for Empire or Jedi, but both movies were shot on better film stock so their negatives have not faded (as bad?).