https://www.npr.org/2012/02/02/146288063/painting-sheds-new-...
about a copy of Mona Lisa that was apparently done side-by-side with the original, and looks entirely different. The article implies it looks the way the original would be, if not for the layers of centuries old varnish covering it. Viewed side by side, the two paintings deliver completely different experience.
I've read a bunch of similar articles about other famous work of arts (temple frescos, Greek statues) - it seems that the old art we see today usually looks nothing like it looked at the time it was made.