I'm currently reading an interview with Kayleen Walters the Senior Director of Marketing at Lucasfilm about the blu-ray release. I just came upon this little snippet and thought I should share:

What are the challenges involved in converting a series of movies that are up to 35 years old into High Definition?

We wanted to create the best possible visual and audio experience for the home audience while maintaining the artistic integrity of the movies. We had previously done a meticulous, industry gold standard restoration when the films were first released to DVD, so we had a great base to start from. We also made some technical improvements from the previous restoration–including some color matching, most notably on the lightsabers–for this release.