[paint guy]

As the OP mentioned, the entire car was sealed in white, except the nose, which was SPI epoxy (a shade of grey). I would guess that if the car and the nose were painted in exactly the same manner (tips, pressure, spray technique, reduction, etc) but the nose wasn't sprayed to full hiding so you could "see" the SPI epoxy thru it, I would think that it would look darker than the rest of the car, not lighter in color.Likewise for the rest of the car over white sealer: not sprayed to full hide would make it look lighter in color than the nose. Thats why I think its either mismatched different batches of paint, or more likely, differences in application. A good chance it can be fixed by scuffing/sanding the bumper, spraying on a wetter coat of base from the same can of paint the rest of the car was sprayed with, and re-clearing. But I woud spray some test panels first.