That bottom row of tile is installed incorrectly. There should be spacers where it comes in contact with the countertop or there is no room for caulk.

The tile has a couple shades gray and the counter really isn’t white. If you try a white grout it will be a new shade. Find a gray that straddles the middle range of your tiles ( blends in ) .

A question you should ask yourself. Do you want the lines to be the thing, or the tile? If you want more invisible, choose close to tile. If you like hi lighting the grid of your tile, then choose darker. For floors, I choose darker. No staining.

Hi @Libby Nasuti. As @SJ E pointed out, whoever installed the tile failed to use tile spacers between the bottom row of tile and the counter for your caulk line. Without it, your backsplash can’t protect your walls, cabinets, and subfloor. The tile has to be removed and re-set properly. When you have it replaced, ask the tiler only to tile out as far as your upper cabinets.

Or, don’t do the side splash at all.