Where does the ONE wire from the centre of the 'rubber' kill switches go? Live(red) or Green(trigger)

Is there no earth on these kill switches?

thanks

That could depend on the bike and so it would assist if you mentioned the bike or included it in your profile - on most bikes the frame is earth (not always) and so the wire would join onto the low tension (thin) wire that goes from the magneto ( etc ) to the coil. It earths the current to the handlebars and kills the engine