How to convert Light Switch from 2 red, 2 black, and ground to 1 traveler, 1 neutral, and a ground?
YOU decided which one was &quot;traveler&quot;.
What you are looking at is a 4-way switch.  It goes in the middle of a 3-way switch string to allow 3 or more control points.  Like this.

Note that this is but one example. There are many different ways to physically route cables in a 3/4 way switch complex.
Now, when you install smart switches in any 3/4 way system, the whole system must be engineered to work together with matching switches.  Generally, the systems for sale in the US make best use of the existing wires, but they use them in quite a different way.
Since every 3-way switch layout is different, you really need to study how the existing 3-way complex is wired, and then adapt wires as best you can.  As such, there is no stock answer for &quot;which colors where&quot;.   We would need to see, at least, pictures of each switch box, and possibly the lamp box as well.
Even more than that, you are re-tasking the 2 old traveler wires to new purposes.  Since you are the one doing that, only you know which color you have chosen to assign to which purpose.
In other words, we can't tell you unless we know what else you did.  Honestly, it sounds like you installed the &quot;master&quot; at one of the 3-way points, and happened to stumble upon a wire combination that worked based on how the other 3-way switches were set at the time. You can't do that with electrical wiring.  You can't &quot;try stuff and stop when you find one that works&quot;, because there are lots of combinations that will work and will kill you.
We see many smart switch products where correct installation is simply impossible in many 3-way routings.  However GE is a shrewd company; this looks like a &quot;remote&quot; switch that takes only 2 wires: a comm wire and neutral, so it should be possible to adapt to any 3/4 way complex.