Assuming it is very green..
Is the TV colour ok when run without any add on AV equipment such as DVD, Decoders connected?
If yes, suspect RGB connections from one piece of external equipment & check for a loose connecting cable.
Then eliminate which item by re-connecting each one seperately.
If no, you need to call an engineer, as the fault in the TV could be anything from a penny resistor, £/$20 colour processor or several hundred £/$ to replace a faulty cathode ray tube.
If it's only a slight tint of green it may be possible to rebalance the colours and/or regenerate an old c.r.t. to prolong it's life.
Cobweb
September 2005