There are least eight different ways to wire a three-way that is not networked. Some of these will work with zwave, some will not. Sometimes it depends on the specific brand of switch that you’re using. So sometimes when you replace a nonnetworked switch/receptacle with a networked one you actually have to change the way the wiring runs.
In the US, wire colors are not mandated by code. People can and do use anything. Sometimes they just grab the last piece of wire in the box before they go home at the end of the day. You can also tape wire which means putting like a little piece of black tape on one end of the white wire. And it’s not necessarily the end that you’re looking at.
So you can’t go just by colors. Or find a diagram on the Internet and copy that.
Even if it looks exactly the same as yours, the current may be flowing differently.
Step one of every wiring project
The first thing, no matter what you’re doing, is to take before photographs of everything, including the screws where the wires connect. Label each wire so you can figure out again later which was which. We all think we’re going to remember what it was like, and we never do. So photograph and label.
Step two of every wiring project
The next thing is to test every segment of every connection so that you know exactly what it is currently doing. (Pun intended)
If you don’t know how to do that, or you don’t know what tools will do that, stop. Seriously. Don’t go any further. Either bring in someone who does know, or go take a class.
Remember your mission
If you live near a Home Depot, many have classes in how to install a light switch, and that’s a really good place to start even if they’re not working with networked switches. You’ll learn a lot about how to look at what’s there and figure out what it’s doing. And how To work safely around home wiring.
Trial and error is a very bad idea with home wiring. Because you can literally burn down your house. Or kill somebody two rooms over. Again, nobody thinks they’ll do this. But it happens.
Remember that your goal is not to turn on this particular switch. Your goal is to turn on this particular switch while maintaining the fire safety and electrical safety of your whole house wiring. That’s a very different project.
I’m all in favor of people learning more about networks, and how network devices can be used in the home. I’m just also in favor of learning it in a safe environment.