A link to the auction would help. I don't know of a black NT, but the NC is not available as a 16 gig device.
B&N.com only has the Nook Tablet for sale in a silver color, but on eBay I saw a 16gb Nook Tablet in black, is it legit?
There are some very nice skins available for the NT if you are interested in a bit of color and variety. I personally like the Skinomi brand skins since they have the nice cutout around the 'n' logo on the back. I've got the wood skins for my NOOKs, but they do have a black carbon fiber version.