Chroma Key (Blue/Green Screen)

How can I change backgrounds in the render to be all blue or all green? So that I can render animations in front of a chroma key background and use in my video editing software.

I am trying to teach myself filmmaking, and now I am in the world of 3d animation (I’ve had Blender since summer 2013 and I cannot seem to understand how it works).

Output an alpha channel so you don’t have to try and re-create it with keying tools (which will never be as good): http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.66/Image_Transparency

If you just want some footage to practice keying with, try these: http://www.hollywoodcamerawork.us/greenscreenplates.html