Wiring light switch with neutral (Z-wave)

Question

I am trying to see whether or not I satisfy conditions to buy Linear WD500Z-1 Z-Wave 500-watt Wall Mount Dimmer Switch. Here is the picture of wiring I currently have:

Wiring of 3 light switches in my box

Inside of the box

Switch box neutrals

Just to provide more info:

I'm looking to replace two left x10 switches.
Third switch, the first one on the right, is a part of 3 way setup and I wouldn't touch it for now.
Wiring situation is quite simple - we have 2 yellow and 1 orange cap
1. To left yellow cap goes yellow (from wall) and black (from switch). Picture can fool you that red is also connected to that cap, but it's not... it's just yellow and black.
2. Middle, orange cap is connected with red (hot) from all switches. I've connected blue from x10 switches to red (probably should have used black, but for x10 switch it doesn't make difference)
3. To right yellow cap goes purple (from wall) and black (from switch)

So, the questions that I have:

Is that white wire in the back neutral that I need for Z Wave switches?
There are two white wires in the back, how do I know which one to use? And do I need to connect each wire to a different switch?
How would I use white wire? Just cut it and then split it and connect to light switch?
How to be 100% sure that white wire is neutral? For line and load I understand that I can buy Fluke Voltage Tester... but can I buy something better that'll tell me whether or not line is neutral?

That picture doesn't show enough of the wiring to tell. If you want a definitive answer, take a better picture (might have to pop out the third switch) or draw a wiring diagram. — longneck, Commented Nov 19, 2014 at 19:05
Agree with @longneck -- we need to know which wires belong to which cables. One of the whites is probably neutral, but we need to know how the switches and cables are related to each other before we can make a good guess. — keshlam, Commented Nov 19, 2014 at 19:28
One more question: What country is this in? Those aren't the most common colors for the US, so I hesitate to express an opinion. — keshlam, Commented Nov 20, 2014 at 1:14
@keshlam It's in US. I know it should be black, white, green (or copper)... but they used one cable with more wires since it connects multiple switches/lights. — nikib3ro, Commented Nov 20, 2014 at 17:18

nikib3ro · Accepted Answer · 2016-01-19 20:27:02Z

Too bad I haven't updated answer when I rewired everything - but better late, then never, right? Here are the answers to my questions:

White wire is neutral in US in most cases... so it was in my case.
Basically, two whites were neutrals for two different circuits. I bought Voltage detector and separated right white wire by turning off circuit for lights - the other white still had electricity running through it so I was able to figure it which white/neutral I needed
Yeah, I just cut it, add in neutral connecting from the switch and then put cap on
For this you need Voltage Meter, there are quite few tutorials on YouTube that explain how to figure out which wire is which with Voltage Meter.

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