If you must paint them now, then paint the color of the walls, so they blend in a bit.

@trailrunner D thank you! I LOVE the marbling idea. The thought would have never crossed my mind to take it in this direction- thanks!!

I think marbling can be very effective in the right place but in this instance I would just paint these the same as the wall color. Very nice staircase!

Sorry, I thought the walls were white too. They should be painted the same white as the woodwork!

Match the wall color: the columns will look more elegant. They are too narrow to be done with a faux marbling effect, which I think would make them look kitschy. Less is more....

They are also not perfectly smooth and that would not look good done in a marble finish. Trying to get them smooth with that metallic paint on them could end up damaging the plaster so be very careful. Your choice whether you do them trim or wall color, either can work.