I agree completely with JayZS. A DVD was released a few years ago - Pure Carp - i think! They showed what happens to different colours as the depth of water increases. The Red colour does go first but the result - as Jay stated is a dark grey - it does not dissapear! Even then you need to get down to 20'+!

This begs, perhaps, a more important question - If the fish can see Jerry's red line so easily - why does he catch so well?

I've long been a believer that fish are less spooked by something they can see and therefore avoid, than something they can't see and bump into by accident. A fish can see the red line so aren't bothered by it - if your using a clear line under the impression it won't spook the fish you could be making a big mistake in your fishing!