* Obviously, no one, including Pantone, can copyright a color, and especially in these days where the RGB/CMYK color systems are freely usable -- ie, you can't put a claim on RGB color "ef9824".
* They can copyright the names and the connection with their inks.
* They want to control the ability of anyone to connect some other color system to Pantone names or inks. My guess is about all they can really do is attempt to keep you from using their color/ink name, as in "this matches Pantone Keepsake Lilac or Pantone 15-2705" (their current color of the day). Understandably they don't want someone else feeding off the system they have created.
* What it really begs for is someone to establish another system (open of course) with its own names which might in some way link up to Pantone and other inks, with the attached disclaimer that no promise is made that this product exactly matches any proprietary color or ink.