At last count 4000. Based on an 11x11 pixel sample of the noses of 4000 photographic portraits taken by an artist.
The samples were then matched to Pantone colors.
At first blush this sounds interesting. On reflection it is just a nosey irrelevance. Why 4K photos and 4K skin colors? Samples shown display many duplicate colors, there should be fewer colors than photos?
All artists know that human skin is infinitely varied as local color and dramatically influenced by surroundings, weather and time of day.
In my experience i can reproduce 4000 skin tone just with the variation possible in PDFs, monitors and printers from just one photograph.https://news.artnet.com/art-world/4000-skin-colors-in-pantone-squares-1254683