Beautiful backsplash! I would probably agree with you installer. But, I have no idea what the correct way should be. I would just like the more uniform look! Good luck!

I'm inclined to say a shade or two lighter than your tile. Can your installer do a couple of sample boards for you?

I wouldn't do white but I wouldn't match either. Then it looks like one monolithic slab of tile material. Decide how much contrast and pattern you want to see then go lighter or darker than the tile color or maybe the gray in your stone. Gray is a neutral traditional choice for grout. Just be sure to get the warm or cool right.

Gorgeous tile - I would stay in the same family albeit a bit lighter.

I second "Gorgeous Tile!" My tiler did 3 or 4 sample of tiles & different grout colors on a board for me. It literally took him about 10 min or less.

Is this the Allen + Roth tile from Lowe's? I used oyster grey which is a close match but does not look monolithic due to the variations in the tiles. I'll try to post a close-up tomorrow but I just posted my finished kitchen this week if you can't wait.

Here is a link that might be useful: Tile photos

Corgimum, your kitchen looks great.
It is Allen + Roth from Lowe's and is called Pearl.
I picked up the Oyster Grey.

Thank you!

Perfect, you'll love it.

I think we have the same tile, we used a lighter grey grout. I believe it was called Snow. I like it very much. Here is ours.