Rear Bumper Color

I've noticed the same with my 2017 Magnetic Gray Metallic purchased new and I believe it's normal and hardly noticeable .

 

It could be:
1) a minor repair which needed a repaint of the bumper - eg scraped by the garage door as it opened;
2) the bumper is more curved than the door, and, particularly with metallic or similar colours, can reflect light in a different way;
3) painting the plastic of a bumper is a different process from solid panels, requiring a different priming process - not sure what they do now, but going back a decade or 2, the top coat was a different formulation - it had to be more flexible as the panel had some flexibility; or
4) something else entirely.

 

I have had both front and rear bumpers repainted.

1. The rear Bumper has a yellow hue to it at the side but not at the rear. Front was painted another time and it is very close but not identical to the the rest of the panels. When i questioned the paint shop they advised painting plastic is difficult and with give a different result from steel panels.
2. Sure enough if you compare other cars and colours you see on the road you will see the same thing.
3. The only cure is to paint it all.