I wish I’d thought of the Gold Toe sock example in this Duetsblog discussion of why Louboutin’s red sole trademark registration, even if valid when applied to a shoe with a contrasting color on top, provides no rights against YSL’s monochrome shoes.  The blue Nike shoe v. the Keds blue mark is another good one.  Our brief talked about red jeans and the Levis red tab, which I think is the same thing, but Gold Toe is just a really clear example.