"The paints used in the reconstructions are chemically similar to the trace pigments found on parts of the surface of the originals. However, those pigments formed the underlayer of a finished work to which they bear a very conjectural relationship. Imagine a modern historian trying to reconstruct the Mona Lisa on the basis of a few residual pigments here and there on a largely featureless canvas.
How confident could we be that the result accurately reproduces the original?
This point is not actually disputed by supporters of the reconstructions. For example, Cecilie Brøns, who leads a project on ancient polychromy at the Ny Carlsberg Glyptotek in Copenhagen, praises the reconstructions but notes that ‘reconstructions can be difficult to explain to the public – that these are not exact copies, that we can never know exactly how they looked’."