With the keyers these days I don’t think it really matters what exact color of blue you get. As long as it’s consistant and contrasts with the actor. I’ve heard that green is better for DV and contrasts better with a human subject, but just as important is the lighting and set up of the shot. 🙂
Make sure you get good even lighting on the screen and try not to get any light bounced onto the actor from the screen. I usually place my actor several feet from the screen and that avoids shadows on the screen and light spill…
Hope that helps! There are a ton of greenscreen (or or better termed “Chromakey”) tutorials out on the net as well 🙂
Jamie