I think it would look ok but not something I would do to my car. Here are a few pics of a white/black kidney grills on a white f11 5ser. I know it's not a 7 but it's the only BMW I can remember with any white trim.
On some of the 2007 750, the two chrome strips that run on the roof and as well the trim on the trunk is body colored while the pillars and window trim are black. IMO it didn't look bad at all like that.
Better still, try doing one side to see what it looks like. You can always strip it back carefully if you don't like it. I remember when in my adolescence, I wondered what it might be like to sleep with a women.....so I shaved one leg!!!
Look for comp-u-cut sign vinyl on eBay. That's what I uses when I did my trim in gloss black. I don't think they have the tape it comes in rolls like 2 feet x ten feet but this to me is easier than the tape.
I can't remember ever seeing the tape in any other colors than gloss/matte black.
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