Y'know, I think this is a common attitude with kids. I know when I was little I thought chocolate was just better, generally, than vanilla, which seemed like plain, or "default," ice cream.
Plaid, however, is not one of your more common flavors. Funny thing is, Schulz has used this joke before. I do think it's common for kids to confuse flavors and colors, a state of affairs that is not, I'd say, helped by modern kiddie marketing.
