You can also use a single LED with a pair of diodes to prevent cross talk, that's what I have on my loop.
Here's a sketch I did for someone, In the first diagram I explain why its no problem with incandescent lamps
The second diagram shows cross talk
The third diagram shows how back to back diodes prevent cross talk, any small diode will do eg 1N4004.
Note: All 12 Volt LEDs incorporate a series resistor to limit the current to 15 mA or less, I haven't shown these for simplicity.