Bench test factory Mopar tachometer

You think maybe you could supply some wire colors? Maybe even some pictures? I mean really, the subscription for my new crystal ball just ran out.

I can tell you this. Normally, tach wiring is......
Red=power
Black=ground
Blue or green=negative side of coil.
Since we don't have a color scheme or pictures, we don't know.

My next best guess is blue and two thirds.