The Harvard Library That Protects The World's Rarest Colors

Even if we go to the 152-crayon case from Crayola, there are certain colors that we just aren't going to ever get to, and I'm not just talking about blurple.

The chemical composition of colors - maybe pigments would be the better word - turns out to be important in identifying the veracity of recovered artwork. Certain pigments come into and out of fashion over the years, and pigments from paintings of already known provenance can be compared to the paintings of those of unknown provenance.

And there's a museum at Harvard University that keeps samples of more than 2500 historically-important pigments.