Just went through this for anyone else stumbling in here well and properly late. Went to junk yard to examine a smashed unit where I could prod and yank at things without worry and that lower facia is moulded as all one piece into the bumper cover and simply textured & coloured differently.
to change its colour you’ll need to tape everything else off and paint just that piece. I did it while bumper still on car and in my driveway in apx an hour with a satin black rattlecan I had laying around.
Did same to mine too. Absolutely ticked me off that the lower facia was a light grey but rest of the ride is white with chrome.
After brightening the other trim around it, the satin finish matched much better.