[Al Skierkiewicz]

The exact process you are asking about in video is called "chroma key". It requires that the camera either output an RGB or component video and that you have an actual chroma key generator to make it all work in real time. You can make it sort of work with a device that will split the video from composite back to component, but that usually add noise that becomes part of the chroma key process. As to the flat light of the background, this is essential as well as it being a flat paint, not gloss or semigloss. Green is a better choice as the video signal in US TV is more green signal than anything else. Blue is the least amount and therefore has the greatest noise when seperated out. There should be no abrupt changes in the geometry, i.e. a green wall and green floor in the background won't work that well. You must back light the subject, to get them to stand out from the background and you must add light as needed to prevent the green or blue background from reflecting onto the subject from behind which will cause unpredictable results.