I don't know IP law that well, but I'd imagine that would be a pretty difficult hurdle to convince the trademark office to trademark colors alone.

I'm pretty sure, for example, you can use FedEx colors together for other than FedEx, and the grocery store is full of store-brand products with the same colors as the national brand.

Besides, do you really want to spend the money trying to enforce a trademark action over some other site for using your *color scheme*? That's like $50,000 or more to mount the challenge, and probably at least several thousand just to file... and if I'm not mistaken, you'd have to be able to prove actual monetary damages to collect anything.