You know, it's funny, but I can't recall where I first heard that Huey, Dewey, and Louie's cap colors are red, blue, and green, respectively. However, I seem to have "known" that since my earliest days reading Disney comics. It used to irritate me no end when Donald addressed a green-capped nephew as "Huey," or a blue-capped nephew as "Dewey," or whatever. Maybe the knowledge is instinctively born in Duck fans? Well, maybe not. But I can't recall picking up the knowledge anywhere; I knew it before I began to see Ducktales, even.