Not sure about who wired it. It really looks like it's original. Just never seen schematics with those colors. Will def have to rewire, most of the wire in it is corroded and won't work anyways, unless there is a break in the wire I'm just not seeing.
Probably will be easier just to start from scratch and use some colors that make sense. Adding a mast/deck light and radio anyways, so whats another couple of wires...
I've been called worse by nicer people.