If I have a black iPhone XR can I change it for a white one?

No.

Hi Disneyland_queen,

You should be able to exchange within a timeframe of 14 days, provided that you purchased the iPhone from Apple (not other retailers).

You can consult the return policy here: Returns & Refunds - Shopping Help - Apple.

Hope that helps!

Patricia

What? Seriously?

You need to sell your it on your own first. Apple doesn't accept trade-ins of the Xr.