How can I change a stone fireplace wall?
We white washed our massive brick fireplace wall. Easy and cheap.
Paint it white, it'll look amazing!
I have seen people plaster over the entire unit to change the look of the stones and then paint it a uniform color. Lots of work, but neat idea.
Porous stone will drink paint and be hard to strip if you dislike the paint job.
You can keep the option to return to the natural stone and make painting easier by covering it with drywall or wood panels like beadboard (or even the uber trendy shiplap:-) Pallet wood would be free, but it would only take a couple plywood or masonite sheets and a few 2x4 for framing.
While you can lighten the color of the stone with paint, you can't hide the texture or irrregular shapes with paint. If you want a smooth stone look frame over the rough stone then set stone like tiles. I have seen travertine look tiles on clearance for $.49 a square foot.
It all depends on what look you want to get. Just a color change or a change of materials?