Your walls have a very yellow undertone. Before you do anything, I’d paint everything the same color as your FP mantle. Then maybe pick a carrarra marble mosaic to replace the green marble. Get some colorful accents in there: art, pillows, etc.

Yes, I don’t like the color of the walls. I see a lot of all neutral rooms, but I think I need some color. I was thinking maybe a very light grey or very pale blue, but I’m not certain if that’s the way to go.

As suggested by Sabrina Alfin Interiors, I would go for a warm white that coordinates with your mantel as well as the marble mosaic to replace the green marble.

Then you can bring some accent for colour into your room, I show blue because you mentioned you were thinking of blue paint but I think it would work better as an accent.

Here's the idea...