my 5700 only seems to support composite tv-out

The card came with a nvidia-svideo in/out y adaptor, and an svideo-composite cable. When trying to use an svideo cable, I get a b&w picture, and I've told the card that I want to use svideo. What's wrong here? Oh, and this could just be the crappy composite cable that came with the card, but colors look really murky and bland - no amount of fiddling with settings under device adjustments seems to help, either...