TBH, I like your fireplace as is. Does the repose gray look nice with your wood trim in your light or is it too cool? Will you be painting the beams and doors as well?

I think it should be the color of the trim

The beams and wainscoting around the side of the room as well as the door and the window frames will be painted pure white.

In that case, I would paint the fireplace the same color as the trim.

I love the trim and the surround, just the way they are. I wouldnt be painting any of them, however, if you are painting the trim, then it all should be the same.

If the room is north facing and has little natural light, I’d limit the gray. It’s going to add to the dull, dark feel of the room. So, in answer to your question, white for sure.