Due to a brief moment of colour blindness, I bought covers for a chair which are totally inappropriate and would like to bring them back
the color did not match to my taste the other furniture in the room.
The time for that is before you buy, not after you take it home, open it and change your mind. It isn't as if you're buying unseen.
Not used is also rather simple - it means "not used", as in "new and untouched".
Yes.