Launch weekend is very hectic for everyone involved. You won’t be the last person in store trying to return a phone that allegedly has a yellow display. You also have people skipping lines, people going into the wrong lines, people making orders for a color and then wanting a different color when they’re in store for pick up. CS issues spike dramatically during launch periods and it can be stressful.
In your scenario, the manager was probably correct. If a customer is really upset about a display issue most of the time they were offered the same. You can open one or two phones in store and see if you like them. If you don’t, they can return it. But they wouldn’t let someone keep exchanging a phone. They’re trying to minimize returns and trying to sell phones. For every phone you exchange you take stock from other customers. And for every phone you return because you’re unhappy with it there are hundreds of other people who would gladly take it.
As a former employee and an avid apple fan, if Apple hasn’t gotten display calibration right in over 10 years they probably never will. It IS unreasonable to expect to be allowed to continuously exchange phones. Anything more than 2 is excessive.
Also I’d like to say I don’t necessarily think you’re wrong or right. It’s just business at the end of the day and they have other customers to think about.