After being convinced by a few members that the Raiders regrade is too saturated, I decided to use a different reference, namely a 1981 publicity still:
Bluray:
Bluray matched to reference (slightly corrected for blue shift):
The sky is now a natural blue, and the colors are very balanced. Interestingly, predicting the frame that was matched to the former reference frame leads to a result that is close to the former reference, without being oversaturated:
35 mm frame:
Bluray:
Bluray corrected:
More in the Raiders of the Lost Ark regrade thread:
http://originaltrilogy.com/forum/topic.cfm/Raiders-of-the-Lost-Ark-35-mm-regrade/