If you’re in Europe, there’s the exhibition on this topic at the Gallo-Roman Museum in Tongeren, Belgium for a few more months, after previous stops at, among other places, the Met:
At least in some cases, they have the side-by-side comparisons you’re looking for (although they obviously don’t have originals of the most famous statues).
A beautiful page on a prior exhibition, with images that allow you to switch between the reconstruction and the “white” look the statues have now after millennia or decay:
If you’re in Europe, there’s the exhibition on this topic at the Gallo-Roman Museum in Tongeren, Belgium for a few more months, after previous stops at, among other places, the Met:
https://galloromeinsmuseum.be/en/see-and-do/antiquity-in-colour/
At least in some cases, they have the side-by-side comparisons you’re looking for (although they obviously don’t have originals of the most famous statues).
Video with more info:
https://www.youtube.com/watch?v=ULQvS-iKNcQ
A beautiful page on a prior exhibition, with images that allow you to switch between the reconstruction and the “white” look the statues have now after millennia or decay:
https://buntegoetter.liebieghaus.de/en/
In case you need an overview of future exhibitions:
https://www.polychromyroundtable.com/exhibitions.php