For the 2016s the Rado Grey wheels are standard and Ebony Black is optional. Silver is gone. The Rado Grey wheels are a bit lighter than the Magnetic paint so they look a bit lighter.
As for the red calipers coming with the grey wheels and not the black... I don't know. The build site says the black wheels have red calipers. I just picked up my molten orange 2016 yesterday with the grey wheels and it has the red calipers. And the story is the same on all 2016 Fiesta STs posted on autotrader. The factory screwed up and hasn't caught it yet. At least not since my car was built.
As for the red calipers coming with the grey wheels and not the black... I don't know. The build site says the black wheels have red calipers. I just picked up my molten orange 2016 yesterday with the grey wheels and it has the red calipers. And the story is the same on all 2016 Fiesta STs posted on autotrader. The factory screwed up and hasn't caught it yet. At least not since my car was built.