How do i make a green screen? What the differnce betweeen green and blue?

Green generally keys better than blue, because the green channel stores less noisy information than the blue channel from consumer CCDs.

I know that some companies sell "chroma Key paint" in the official colors. If your actors are going to have much green in their costumes, use blue. Otherwise, stick to green.

your also going to need either a switcher with chroma key or probably avid, final cut pro or adobe premiere to do it