Possibly both. Marine Collectors was selling them as yellow but they've discovered that BA is growing out both their grey bellies and yellows in the same tank. Since they look the same as juveniles there is a chance that yellows will be grey and vise versa. Marine Collectors has changed since they discovered this and are only selling them as captive bred regals not specifically yellow bellies.
Eliot offered me my money back and I got a personal phone call when he discovered the issue. We're happy to take a chance to get a captive bred and BA believes they know which are grey and yellow in the tank.