Green bikes, especially as per the OP are handsome and could probably survive a black colored crank. That said, per post
#2 ; a dark grey would look good with a black crank but one shouldn't overemphasize one part of the bike, the crank. I have butterfly bars on one bike. White wrap looks good with green as well.
Mettalic green or as the caption to the photo says, emerald city? It doesn't matter too much, it's in the general area of the same color.