Did they color grade the Blu from scratch, though? I thought they used the DVD SE masters as a base, and just fixed some bits and pieces.
In 2004 they scanned in the negatives at 1080p and graded them to that over-saturated-magenta disaster that we’ve been stuck with ever since. There may have been some tweaks in 2011 for the bluray, but the fact remains that all three movies were graded from scratch in 2004.
Having gone through the entire OT and PT frame by frame, when doing my HDTV releases, I can tell you that the only film with significant color changes for the Bluray was Episode II. (Of course TPM was a completely new master. 😉 ) Definitely not re-graded.