I did wonder about that, but mine normally turn a green colour over the
winter. It did strike me someone might have done the lot with one big roll of brown
rope.
I bought a kit car like that once. Fibreglass body so pos and neg wires needed rather than just using the body shell as the earth return. Yep the first owner wired the whole car in black

Trying to do a temporary re-wire at the side of the road after a small
electrical fire was fun.
Pete