No the green wire to your rev counter shouldn't be live. It basically carries the negative fly back pulses from the primary coils. As you have two coils you'll need to combine those pulses

I'm guessing the green wire in the cossie loom is Clean Tacho Out (CTO). This can probably be read by a Cosworth Rev counter but most of the ERST ones won't read it. Your best bet is to run the diode circuit in the EFi upgrade sticky thread.

Lee