The green screen could be a short inside the cathode ray tube (in which case you often get one excessive color with flyback lines), or possibly arcing elsewhere has damaged other components, eg. video processor.
Otherwise, arcing could be anything from a loose connection or socket - (simple), a split high voltage disc capacitor arcing - (cheap), to a smouldering printed circuit board connection - (dangerous).
Or breakdown of insulation to EHT components - (expensive).
It really should be inspected by a qualified engineer for safety. All are potential safety hazards and often faulty parts require replacement with the manufacturers original 'safety specified' components.
Cobweb, January 2005
