There are very intersting informations in the Legacy thread. Mike Verta explained that his technicolor scans were made to capture maximum data from the prints and still needed to be corrected to recover their original look. And Harmy used the raw scans as reference for DE v2.5 (or 2.0 ? I have some gaps in OT-history…). Plus, as he said himself, he worked on colors to match the scans but not on contrast.

http://originaltrilogy.com/topic/StarWarsLegacycom-The-Official-Thread/id/1418/page/39