In a gangbox with switches on two different circuits, how can I identify which neutrals are associated with which circuit?

By 'two different circuits,' I mean 'two separate single-pole breakers'.

Here is a crude wiring diagram of the switches and electrical box in question:

• The red things are wire nuts.
• The black ovals (1-6) are knockouts.
• Circuit X:
• Switch A is a single-pole switch that controls 4 outdoor lights.
• Switch B is a 4-way switch that controls 2 ceiling light fixtures (along with 2 other switches).
• May also have 1 outdoor outlet, but I forgot to check.
• Circuit Y:
• Switch C is a 3-way switch that controls half of an outlet (along with 1 other switch).
• Also has 4.5 'always-on' outlets.
• The pink wires in the diagram are white in reality.
• The black connected to Switch A is the hot.
• The pink (white) wires never measure a voltage, regardless of any switch's state.
• I have a very basic 2-probe voltage tester (like this), but no continuity tester.
• Everything functions correctly.

What is the easiest way to figure out:

1. If the pink (white) wires are indeed neutrals?
2. If they are associated with Circuit X or Circuit Y?
3. What the orange wire is? (Possibly neutral for the other circuit?)
• In a box containing switches, it's very common for all the neutrals to be bound together the way the pink wires are in your diagram. As far as "which neutral for which circuit", in the breaker panel, all the neutrals are connected to the same bus, so what are you really trying to figure out? They are all connected electrically. Commented Oct 1, 2015 at 20:07
• What is the actual color of the orange wire in your diagram? Commented Oct 1, 2015 at 20:23
• The orange wire is actually orange. Also, I was under the impression that each circuit has its own neutral, that they cannot be connected together on the 'house' side of the breaker due to the risk of overload, and that the only accepted way to do it code-wise is to use a dual-pole breaker with a MWBC. Commented Oct 1, 2015 at 20:34
• Ah, I see what I missed - you know that the wires in this box are for two different breakers. I've never come across orange or yellow wires in electrical boxes. What part of the US or other country are you in? Commented Oct 1, 2015 at 20:45
• Can you diagram the other two 3-way switches that work with that 4-way switch? The orange wire probably goes to one of the 3-way common terminals. Commented Oct 1, 2015 at 21:28