Colors appear to be added by the restoration process. This kills originality of the works. I would prefer to see an artwork as it was created, not "enhanced" in anyway.
The artwork "as it was created" is unavailable. The only options are Rougeoux or the ravages of time.
Incorrect.
The original scans with faded colors and yellowed paper are also available: https://www.c82.net/naturalists-library/sources/scans