After the restoration of the Sistine Chapel, a number of art historians were shocked at the results. Many had assumed that the darkened, muted palette they were used to was intentional. (A few examples: [1] [2])
The restoration of the Ghent altarpiece by Jan van Eyck changed the lamb at the center of the piece in a way that lots of people have found... bizarre and slightly disturbing [3].
And the strangest example is probably Greek architecture and statuary, which we today consider to be the height of dignity and gravitas, but were originally brightly painted. [4] But if we were to paint the Parthanon bright primary colors like the Googleplex, would we be recovering something or losing something? It feels like a bit of both.
[1]: https://external-preview.redd.it/I4wkSd0S_hGySQbGLAtITMMPJq-...
[2]: https://en.wikipedia.org/wiki/File:Gardenbeforeandafter.jpg
[3]: https://www.bbc.com/news/world-europe-51205614
[4]: https://www.bbc.com/culture/article/20180119-when-the-parthe...