Spoke to a buddy who works at a local Chevy dealership. They order the paint directly from GM so they will use the same color as was used at the factory. "The service guy will get the paint code from the plate." I would assume the plate is his way of saying the door frame sticker or something similar? You should see no difference in color what so ever. If you do then take it back and have them do it again until you're satisfied. I agree with the previous poster that they should re-finish the spoiler as well just to be safe.
He said it's a three day job at the most. One day to remove, clean and prep the deck lid, one day to paint and one day to cure, sand and shine it up.
"Ladies and gentlemen take my advice. Pull down your pants, and slide on the ice."
"E for electricity... V For Chevy Volt and me!"