Can I change the color of my iPhone

Only if you're within the store's return period or you sell it to someone else; if desired, buy a case in the color you want.

(261992)

That is a great question or Apple but they do not participate here.

This is Apple's return policy that applies only to purchases directly from Apple, either in their retail stores or their online store:

Returns & Refunds - Shopping Help - Apple

If you bought from any other seller, the sellers's return policy is in effect.