Does Amazon actually have something that tells them if a B/G is not "FFFFFF"? Of course, I see very few items with a B/G. Most of the photos are just of a blu-ray or CD cover.
It was in the image requirements. All the main images I've seen of items from can openers, etc. are plain white. Probably cut outs.
Did you actually try to upload the original and have it denied, or is everyone dancing around here because you're treating Amazon's suggestion as the 11th Commandment? Next time, use a flash. White is white.