Are you sure you want to sell it? It's a very good saddle & might be a fine back-up to have on hand in case at some point you want to try something different. I don't know what you ride currently, but if it is narrow then you are in the same ballpark with the Arione as it is narrow & flat.
Also, if it has never been used, have you tried to return it to the retailer? I know most have a 30-day return policy, but most will be flexible on this if the item is still brand-new & re-saleable. Might be worth a phone call.
I wish I had seen your post earlier -- I just bought a funky acid yellow Arione as a back-up for my trainer bike because it was a very good price & for a bike I keep in the basement, color was a secondary issue. Given the choice, I would have preferred your black one.