I might consider eliminating the mantel as it's too short . Once there are other items around the fireplace you will not focus on the slate color tones that you don't like.

Not sure what your budget is for changes, but it looks to me as if most of the orange slate is near the top. The bottom part is mostly blues. The orange colours are further being emphasized by the light over the fireplace. I'd unscrew that light bulb, and put a large piece of art over the top of the fireplace.

A dark wood glaze over the mantle would be much easier than trying to lighten it, which will involve stripping it to bare wood. Or you could put a mantle cover over it. (Also called a mantle cap or slipcovered mantle) They go right over the existing mantle. Here is one of many how-to's. Or you can purchase them.

I agree that the mantle is a bit high but it's probably a fairly complicated exercise to lower it.

Another option is to drywall over the top part of the fireplace. That would make it fairly easy to add a lower mantle because you would be covering any holes where the previous mantle was attached.

If you want to change the grout colour I'd go with a medium gray, not white which will make the individual tiles stand out in an odd way.

I wonder whether you could just glaze over some of the brightest tiles to dull the colour. Get some watercolour paint or thinned-out latex wall paint in a medium/dark gray, and just wash over one, and see if it looks better. You can always wash it off if it doesn't work.

Honestly I would take the slate off and get some Grey tile and only go about 2ft to 3ft above the fireplace and place a mantel there and paint above the manual but give the manual an old rustic

Wow! Thank you all for the feedback! such good ideas. I failed to mention we are renting but possibly buying it in about 2 or 3 years. So I cant remove the slate. Also, I can remove the mantle but I cant remove the posts that hold the mantle. They are built into slate and wall. See Picture. What if I bought a longer mantle? And what color? i would paint the posts to match it and make sure it is longer. And changed the grout to grey as suggested above? I am just so stuck since I am renting right now but I can’t wait a few years. I am a very visual person and since this is the focal point in our living room it is bothersome. Thanks!

Do you have black in your room as possible color for a new longer mantle?

Check with your landlord before you do anything that can't be put back exactly as it is, such as painting the grout.

Lisaam I do not have anything black. grey couch and getting new chairs once I figure out what to do with fireplace. The floor is also getting done to more of a brown with grey undertones so it wont have that orange color. We are getting a smaller tv or possibly not going to have tv in this room at all. i want it to be cozy but not busy.

partim Thanks for the response. we would never do anything not allowed. We always ask for approval first. Thanks for feedback.