COMPLAIN COMPLAIN COMPLAIN.
Take the bike back & speak nicely but firmly to staff until you get what you want. Quote the R&G site, take print outs. Phone R&G & confirm if indeed the black is an 'extra'.
If you stand your ground long enough they will back down & change the silver spars to the black. If they didn't tell you that the spars were silver I'd mention it & use it as a bargaining tool. Okay "you should've asked" is what they'll probably say but the pictures you saw were black & THEY never told you otherwise.
You'd expect a dealer to know this & be upfront with you.
Good luck & keep us updated.
Don't settle for anything less that what you want.