I know I keep banging on about this, but...
1) The IB Techs are all too green, Senator print included.
2) Photos from on set are mostly useless, different film stock, and most likely balanced by the photographer for his own 'look', and usually will tend towards neutral tones, usually will have nothing to do with the look the DoP is going for, and will be completely different.
3) Photos taken of screened movies (e.g. the Senator photos) are almost completely useless, the camera used will most likely blow out the highlights and the white balance setting on the camera will completely change the colours.
4) The Home movie releases all have their own colour problems, and are taken from (generally) a faded source, and have completely different exposure settings to the films.
5) There is no 'original colours', the Tech's are all greenish, the Kodak prints have all faded to red, the LPP is of questionable heritage, and the original grade of the film is all over the place anyway.
6) Every print, and every screening would have looked different.
Star wars is fairly neutral as far as the grade goes, so research into costumes an props can help, but one as to be careful, as they may have been purposely lit to look a different colour.
I'm really enjoying the tech behind all of this, being able to match the look of on version to another is really useful, especially with faded prints, but grading Star Wars now is really down to the individual.
The only things we know is that Darth should generally be black, the stormtroopers white and the skintones in most scenes should look natural, and the laserbolts red and green, and space as black as possible. If the troopers have a colour cast during 'outside' day shots, and there is no obvious source for the cast, then it probably needs fixing. If the skintones aren't right and they are not, say, in the trash compactor for example, then it probably needs fixing. If the makeup is overly visible then the saturation needs adjusting.
The rest is down to knowing the era, the film stocks, finding out as much about the shoot as possible, and having a light touch. Every print, and every screening would have had somewhat different colour, there is no original colouring as such, so our job now is to get something that doesn't look 'wrong' so that effectively, the colour is not noticed and just serves the story.
Everyone will have different opinions, those that grew up on the home video releases, or the newer more contrasty/punchy films will probably find a grade that is closer to the originals to look odd.
There is no right answer, but if the skintones are off, or you have tinted troopers, then you are probably going in the wronf direction.
The Program Dre is doing is great, as you can effectively pick a look, and then use that as the starting point for a full grade.