AntcuFaalb said:

Lazy question: did the color inconsistency originate on the LD itself?

Yes. The problem just got magnified with my adjustments. Side 2 and 3 are extremely inconsistent in places. Just take a look at the first scenes in the trash compactor and see how bad the contrast and gamma is compared to when we later come back when the walls are closing in. The Death Star battle at the end are the worst, there you have a very frequent inconsistency in levels where some shots even appear desaturated. If you really want to check how inconsistent the levels are there, check the scene where Vader informs the TIE pilots "Several fighters have broken off from the main group, come with me". Almost night in that scene. ;)

EDIT: Sorry, I misunderstood your question. It's probably an IP in bad shape that is the reason for some of it if I would make a guess.