@Felthry You can trademark a color by claiming that your brand is distinguished by it. Coca Cola's red, McDonald's yellow, UPS's brown, Tiffany's blue - all of these are trademarked.
@Tathar @Felthry You think wrongly. https://en.wikipedia.org/wiki/Colour_trade_mark#United_States
Oh, this is why I thought that. https://tmep.uspto.gov/RDMS/TMEP/current#/current/TMEP-1200d1e1975.html
(Important to note that I'm saying this in the sense of "should be" rather than "is." I also think that orange in the context of peanut butter cups should be considered aesthetic functionality and ineligible for trademark protection because people prefer peanut butter that is colored orange.)
@Felthry @lorxus
Maybe the UPS brown because they use it in their slogan, but I associate red as much with Walmart's Sams Cola as with Coca Cola. I wouldn't associate either of the others with any particular color.