it's not really green screen..it's actually known as 'chroma keying' where you made a particular color transparent..so it can be any color of the rainbow but blue or green work best in most cases because they aren't close to any human skin tones

try jit.chromakey

very important to have nice, even light in the whole area. The inevitable shadows will be just a bit away from the main color you're chromakeying out, so there could be some "fuzz" where it's sort of halfway removing it. It's tough to get it totally precise. And yes, ant clothes people are wearing that are that color will become transparent. Which could be cool, have someone wear a striped shirt with that color, or have some body paint to mess with :)

I got fairly good results using a projector on "standby" mode which was a nice rich blue, we wore black and moved around in front of it, pretty good keying out. Reversing it was fun too, so the silhouette was removed instead... this is why we wore all black, so we could set the key color to black and get the reverse effect. The light from the projector is nice and even too.