Hello, I have 6 zone valves in my cellar, near the oil boiler, and my tarm is 50 feet away in another room. I'd like to add little (red?) indicator lights so that I can visually tell if a zone valve is open or not. If possible I would add on right near each zone valve, but also run pairs of wires to a "status panel" near my tarm so that when I am tending the fire, I can tell which and how many zones are calling for heat. My zone valves are pretty standard, picture attached...what is the simplest type of bulb I could put across which wires to see the on/off status?