Secondly, Hoth was always blue it was never white. Check the original film sources. Yes snow is white, but when lit it looks blue. Are the scenes in D+80 too blue? Maybe. But Hoth was never intended to be white even in 1980.
Actually, that’s not entirely true. Hoth snow was always meant to be white. Gary Kurtz said how hard they had to work to maintain the white colour of the snow while filming. When it came to duplicating the film for theatrical release, the process got screwed up. causing a heavy blue boost and shift. Gary said that the only time that Empire was ever screened and had the correct grading was at the 70mm premiers. While the 70mm release prints didn’t suffer the overly blue grading the 35mm prints were nothing like they had originally graded the film. The same thing happened with ROTJ. Most people would have seen ROTJ with a very heavy blue tint to it due to botched the duplication process. Compare a 35mm theatrical print with say a 35mm show print and you can see the difference in colour.