Don't companies trademark specific colors all the time (or at least try to prevent those colors from being used in anyone else's corporate logo)?

No, or at least I believe it's more complicated than that. A logo's trademark may encompass the colors used, but that's not a legal maneuver which prevents those colors from being used anywhere else. The point of the trademark is to be able to stop competitors from making "confusingly similar" trademarks for their products or companies. I can make a cola, and I'm certainly not enjoined from using red and white in the colors on my can. If, however, I make a red can and put "Boba Cola" on it in white letters with roughly the same typography as Coca-Cola uses, I'm cruisin' for a bruisin', legally speaking.