Ok as far as the color change, a White's will be brown against a dark background and green against a light one. They are never gray or red, and the lady who told you this is talking out of her ***.

As far as getting your frog a roommate, it doesn't really matter. They are not social, nor are they territorial. You should quarantine any new frog before introduction to your old frog. Also with the conditions the frog came out of, it might be a good idea to get it checked out by a vet.