Real men don't need labels and documentation.
They're the wiring equivalent of reading the instructions. A real car guy can look at any bundle of wires and instinctively know where to start messing. And you don't repair so much as keep adding new stuff until it's all better.
My VS was delivered new to me obviously wired by some true car guys. The telltale hints were everywhere. Like in the engine compartment where a green wire was led to a cleverly hidden spot behind a bunch of other stuff and then butt-spliced to a purple wire. There was no reason to do that other than to throw off wusses who rely on color codes and labels to figure things out.
I'm a car guy. I just knew the purple wire and the green wire were the same one. Developing a feel for this kind of stuff can take a lifetime.
But it's under the dash where the 'car guy' school of wiring reaches high art. A mysterious, thick bundle of wires emerges from under some carpeting and then immediately disappears up and behind a steel crossbeam, where it's tightly zip-tied in place. Most of the wires from the instruments and panel switches are led into the same blind space.
You can play with lights and mirrors as much as you want, while lying upside down on the floor, clutch pedal jabbing you in the ear, but you will never actually see what is connected to what up there. Color codes? Labels? Seriously?
Wiring and wiring repair on my car is done by feel and intuition. If you can't follow a wire through the maze to its source (about half the time), it's best to cut it off and wire in a new connection. The more wires, the more impressive it all looks when you're done taping it back together.
Labels? Nah.
Car guys just remember what everything does.