The biggest change in ESB was the color grading. Where Hoth was originally white, in the SE it is blue. I am torn on the change, because I grew up with the SE color grade and I never hated it.
This is actually not true. The Hoth sequences were originally blue theatrically, but then turned white for the subsequent home video releases.
I did not know this. Is there a way to know just how blue the original sequences were? My prevailing impression is from the VHS releases circa 1992.