Paint / remove paint from bumper (Volvo 850 Limo)

Hello together, with my moose the previous owner unfortunately tried to color the front bumper somehow – in black. At least that’s how it looks. It’s definitely darker than on the sidebars and at the rear. There you left it to be lucky, after the front was probably only so moderate in the result. I have already treated the rest of the parts with Koch Chemie PSS and am completely satisfied with the result. Now is the question: Does anyone have an idea how/whether to color / the la ck gets so removed that the bumper is still to be used afterwards? Ideally, looks like in the original state of course. With what means was treated here unfortunately is unknown. I once attached two pictures. The greyish parts is original. So part of the coloring has gone away at some point. Greetings!