Fragging colt coral is very easy.
I just made a couple nice 2-3" ones two weeks ago.
Take a nice clean razor blade and cut off a "branch" just below where it forks. This will give you a nice V, to elastic it to some LR so it won’t come off. Don't bother trying to glue the colt to the LR. It won't hold for more than a day or two. Believe me I have tried. Where you have taken the cutting from the parent colony you will see many small exposed circular filaments. These will form the pharynx for new polyps, which will become visible within a week or less and full-grown in two. It's quite amazing how quickly they recover. Your frags will take a couple weeks to attach themselves as well.
Good luck
Evan.