Take it out.. I had a similar thing happen. I added the same fish to my tank which already had a fox face in it. The fox face wouldn't allow the bi-color to have any peace. So to make a long story short. The aggressive one went back to the LFS... I still have the Bi-Colored.
I used a fish trap to catch the problem fish. It worked pretty good just took some patience. Place the fish trap in there and just let them get used to it. Put some food in there and let them feed out of it for a while. Once you get the fish in there you want pull the string and it's caught.
Another thing is to catch it after the light go out. Figure out where it sleeps. sneak up on it and net it out.