What paint sheen?

Match the finish to other mouldings in the room like door trim, base boards, etc. I like semi gloss latex wall paint as opposed to enamel. Much easier to apply. FWIW

Dont see why this has to be asked....its your house, paint it whatever finish you want to. We dont have to look at it.

I think he's asking which finish will render the best sonic advantage.
I have no clue. But I can't believe no one here has an opinion.

If you had unlimited finances finish the columns with Anti Vibrational Magic {AVM} it works. Next would be a spray stone paint finish available at the Depot or Lowes. If the columns you have now are of the right angle type remove them and replace with the following. The rough stone finish on a tapered or sculptured column will have random harmonics travel along its irregular surface versus those of a smooth finish on a perfectly symmetrical column which may generate a more singular resonance or peak. Tom

I'd use flat. It won't reflect the light from the TV and create a glare. Several manufacturers sell a "ceramic" or likewise flat paint that is washable/durable, unlike most flat wall paint. A multi-color textured paint such as Multi-spec or Poly-mix would give the columns more of a natural stone appearance and have a flat finish as well. Most of the multi-color coatings must be spray applied, however.