My guess is that the green tint may have been a mastering mistake but the over-all colder color palette was probably intentional. Plus as far as I know, they never admitted there was anything wrong with the colors, so I wouldn't expect a fixed version any time soon - the films came out as individual releases since, which would have been a great opportunity to fix the colors, since even people who have the boxed set, could just buy FOTR separately but that would mean they'd have to admit the timing to be wrong and then people could demand a replacement. And to market it as a remaster would be weird too, since the original EE BD release was already marketed as a remaster.