If it is the same as on my 42ds, it lights the orange ‘running’ led by the switch on the main panel. The idea is to give a visual indication when the pump is running to avoid letting it run on empty (which is relatively quiet)
I just installed a new pump and traced all the wires, and compared to wiring diagram.
On my boat it goes from "50" a plug on your switch/breaker panel, an orange wire. It runs to a standard relay mounted next to the pump. In my case it was wired this was, bypassing a wire on the factory Johnson Pump. When I installed a new, bigger pump, I eliminated the relay as there was already an output wire from the pump that I could connect directly to and maintain the indicator on the panel. No reason to disconnect it unless you don't want the green light on your panel.
I can't visit my boat to check but pretty certain that an orange wire marked 2P1B goes to connector 50-9 on the Scheiber multi-display and not connected at the other end. It is for an optional 3rd water tank if that's the wire you have found. Makes sense if they meant LCD instead of LED
I built a new multi-display a few years ago (2 arduinos and custom IO board). My notes say that pin 9 on connector 50 is orange and marked 2P1B.
A third tank would need a box (50.BTE05000E.00) with 12V +ve, -ve and the wire you have found. I didn't intend to fit a 3rd tank but would build 50.BTE05000E.00 for a tiny fraction of the Scheiber price.