Colts are pretty hardy, I have a few and have fragged them several times by just grabbing some scissors and cutting them off. They shink up for a little while but mine have come back full in as little as a couple of hours. I also have had them adhere to two different rocks and I just pulled them apart. Some material was left behind and just started growing a new coral. So in my experience you should just go ahead and gently pull the rocks apart. If you want to be extra careful and not leave any behind you could try to lift it up from the edge and pull it off the rock, or just take your scissors and cut it away and start a new coral.
