There is a difference between having a part being painted at the factory vs at a local body shop. At the factory, they should be able to get a factory painted part, which should be very, very close to the paint on the rest of the vehicle.
If the local body shop has to do any repainting, they will likely have difficulty completely matching the paint job. When it's just a spot repainting, then can smooth out the transitions so you probably won't notice the slight difference in the paint. But if you get an entire body part, that's harder to do - and you may always notice a slight difference between that part and the adjacent parts.
When our 2013 S P85's rear bumper was replaced, the bumper color is very close, but not exactly the same as the rest of the car. If you look closely, it doesn't completely match. The body shop offered to make another pass at repainting it, but they couldn't guarantee it would be better. They could also try to do some repainting of the adjacent parts to smooth out the transition. We decided to accept it as it was - rather than risking having them do something that might look even worse.
We're hoping to get our X late today or tomorrow - if we see any damage requiring replacement of a body part - we'll ask for a replacement vehicle. If there are any scratches or dents that can be repaired in place, we'll likely accept that (which dealerships without your knowledge, prior to delivery).