I can't think which Panasonic model uses a green led, so I assume it's not a UK model. However, some models use both red and amber led's, indicating either standby or timer mode.
If your TV has any built-in timer features (eg. UK DVB models have an integrated programme guide & timer). Check that no programmes are reserved in the timer.
Also, I'm assuming yours doesn't have an integrated video recorder, if it does i'd also check clock & timer settings first.
Otherwise, a constantly flashing red standby LED on CRT models usually indicates the set is in protection mode due to a fault and will remain that way until the fault is corrected.
It can be caused by many things and so you'd need to take it to a service centre.
Cobweb, July 2006