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I believe there is a 14 day return window and possibly a 30 day exchange window, assuming you bought it from Apple. I exchanged a space gray for silver.
 
Provided that the Apple store has the one you want in stock, you should be able to do an exchange and yes you have 14 days. Of course once you do an exchange you get another 14 day window as well.

Do not worry, Apple reps do not bite and they are very friendly and they will be very happy to assist you with your needs.
 
What do I need for an exchange? The receipt?

Also would the AppleCare+ be carried over to the new phone?
 
What do I need for an exchange? The receipt?

Also would the AppleCare+ be carried over to the new phone?

You will need to bring in your original packaging and the receipt as well (although they do scan the barcode). I'm sure Apple can transfer the applecare+ as well.
 
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