Wow-I am amazed that you remember names like that mom2reese! It is Lunada Bay Sumi-e but ZUSHI Natural. I picked it out from a small card sample and there were no blues on it so I was taken aback when I first saw the real thing. But I like it and I have that blue in my room luckily. I am not sure it goes so great with the granite hearth which was a remnant slab, dark brown with reddish/copper but I think the copper grout should help with that. We had to order some more is why we stopped here! Now I am thinking about going up to the mantle bottom and then maybe a band of 2 or 3 around the top of the mantle rather than the whole shebang. I would love to have something that sparkly for backsplash, will be looking at those again.

Actually, the link is correct. That's the right picture. I did try to contact the designer via Houzz but she was not commenting back. I then tried her website, but it was under construction. So when all else fails, pick up the phone and call the designer :) Thankfully she is in my area and directed me to the store where the tile was purchased. She told me it was a 1/2" x 1" gray stone. She didn't have the exact name, but with the help of the gal at the showroom, I think we found it. It has both the grays and the tans I'm looking for, has the classic but casual feel and goes with all the "potentials" for my kitchen choices. It is called Nova Blue by the Quarry Collection. Here is a picture with my floor and two of the counters I am considering Caesarstone Pebble (L) and Caesarstone Shitake (R). It also looks good with Mocca Juperana (granite) and so many other options! What do you think? (my "inspiration" pic is linked in my original post)

If you go the grout colorant route, first do some estimating on how much coverage you'll need. Do a rough measurement of the length of all of the mortar joints, then multiply that by the average width of the mortar joints. Convert that to square feet/inches, whichever is more appropriate. In my opinion, the best grout colorant out there is Aquamix's. It can color white grout black, or black grout white, with no color bleed-through. It would be a tedious application, though. Once you have calculated the rough amount of surface area that you have to cover, I'd call Aquamix's tech department and ask them how many bottles you'd need. Another avenue might be to acid stain the existing grout lines. Depending on your application skills and the quality of the existing mortar joints, acid staining results may vary or coloration may be slightly uneven. Also depends on the age of the mortar, it's cleanliness, etc. Acid staining would likely be easier, I think, than using the grout colorant, but I believe that the grout colorant, due to it being a topical layer rather than a stain, would give you more uniform results. Kind of along the lines of painting a piece of wood (predictable results) versus staining it (possible blotchiness). Still, you'd want to clean the existing mortar prior to doing any coloring. Mongo

Are the tiles installed horizontally around the fireplace opening? If they are, the spotting may well be from wood sap spitting out from the fire and landing on the tile. The spotting would be heaviest near the fireplace opening if this is the case. Should be relatively easy to fix by cleaning with paint thinner or similar product.