changing my replacement screen iPhone 4S

Apple does not modify hardware for users.

what do you mean does not modify hardware for users? , even if i bring my own pink iphone parts i ordered online? they wont change the white to pink?

Apple repairs hardware with Apple parts, not parts you bring to them.  Did you order the pink parts from Apple or another source?

another source , but it says apple on  the  back glass

That does not make it an Apple produced part...there are no replacement screens in the Apple on-line store for the iPhone.  You can take the iPhone and parts to an Apple store and ask the genius bar to do the work but it will be a surprise if they agree.