My Thoughts:
1. You need to distinguish between more current images and the PGF, so you can try to define the color variability in fake furs. in 1967 fake fur was pathetically unrealistic in general. I didn't see any really impressive natural-looking furs until around 1976, when Rick baker showed me a color swatch of premium fake furs (for fake fur coats) from Europe, but you had to buy the fur a bolt at a time, minimum, which was enough for 10 full suits, so out of the price range for your average creature maker or hoaxer. Fake fur rose to very realistic levels in the mid 1980's with National hair technology (now called National Fibre technology) custom weaving fake hair strands into a spandex base. I has them do so very complex color blends, and they succeeded splendidly. By the mid 70's, they also had course guard hairs and base fur combined for a more natural look.
2. Where experimentation might be worthy is testing real and fake furs under daylight and open shade outdoors, to see how each photographs. One example of a test would be to take a taxidermy full body figure (using the animal's real pelt) and then take an identical manniken and dress it with fake fur to match the real animal as best one can, and photograph both side by side under same lighting. That might reveal differences that can be quantified. Something like the attached image, the two upper right photos of a real chimpanzee and a fake one, side by side.
Bill