If I understand you correctly, you have a TV set that could be getting its video signal from an internal tuner or from an external source. You wish to drive RGB LEDs to create an ambience, like some Philips TV sets.
Question: does your TV set have any kind of RGB output? Of course, things are changing fast in this digital era, but it is not inconceivable that you may have this. If so, your problem is almost solved.
David