There is no way in hell that bumper wasn't sprayed.It is possible that the bumper was sprayed - It's hard to tell. As crazy as this sound... Humor me, all Volvos, and many other cars' rear bumper have a slightly different color depending on the lighting. Apparently it has something to do with the cross traffic radar (I am not sure about this part). Take a look at random Volvos online, it will blow your mind, and once you see it, you can't unsee it
Probably farmed out to one of those mobile airbrush companies that "fix" bumpers on the lot.