I don't buy that the colors are rare. Maybe just the process that creates them takes rare materials or a lot of time to develop. We now have display units that offer millions of colors. I'm sure some cover his "rare" color collection.
Its much like stupid websites that say "rare WW2 photos" or some other such crap. WW2 photos are not rare, the subjects are often not rare.... And once they are digitized and put online everyone with an internet connection can now have copies of those photos. Where is the rare?
I'm a lover of music. There is something lost in the digital recording of music... It's not as rich as either a live performance or a LP record. I can hear and follow a second flute in an orchestra listening to the William Tell symphony live or on records, but I can't follow it digitally, something most people aren't sensitive to is missing.
Although my visual accuity isn't nearly as good, regulating colours to a hexidecimal code is similarly limiting. Luminosity of paints are poorly translated digitally as well (colours in a painting changing due to angle and light source because the paint is slightly translucant with an underlaying layer that s subltly refracted through the exterior layer). Perhaps easier to understand would be the complexity of using gold foil in a piece of art. Take this Klempt:
The painting is filled with flourishes of gold leaf, yet digitally it looks flat and inert. Even the depths of the flowers are missing in digital format. We may have come a long way digitally but we still haven't reached the resolution of actual film,never-mind the subtleties of real pigments.