@ R2-D2: It's a deliberately new colour timing, and reflects a number of things. Some of it is faithful to how the films originally looked. Some of it may even be faithful to how Lucas wishes they did. And a lot of it is how Lucas thinks the films should look today (eg., not exactly the same as before).

The 1997 Special Edition was actually pretty faithful to the original versions in terms of colour, with few exceptions, and was matched by YCM Labs to a 1977 Technicolor print of Star Wars (not sure about the other films). This was on the IP duplicate prints, unfortunately, so when they went back to the original camera negative for the 2004 release none of this was carried over. That's probably one reason why George decided "fuck it, we'll just give the films a whole new kind of look." They better match the cleaner, high-contrast, more colourful look of the prequels, so I am guessing that was one motivation for Lucas to screw around with the colours. He guided the colour correction himself, after all.