1) Today BMW takes turns in making the earlier-style kidneys, one run will be all silver, the next will have black slats.
2) The later style (bigger, clunkier-looking) kidneys I believe all had black slats, I do not know if they are still available from BMW or are now NLA.
3) Silvered wing and hood grills were pretty much early cars only, I've never seen an original 2800 with black ones, regardless of body color.