Grey Tile With Black Grout

Which dark grout with white subway tile for kitchen?

We are renovating our old house but still wanted to maintain an older, charming feel for the kitchen.The floors are slate (dark charcoal) - but covered in cardboard at the moment; countertops are white (Silestone Eternal Statuario).

Knobs and some accents are dark burnished brass; appliances are stainless steel.I know the grout won't look uniform on the tiles, and I'm OK with this.Tile will also go on the wall to the left but nowhere else in the kitchen, making this large wall the "feature" wall.

White vintage metro tiles and black grout in a bathroom.

Tiled white shower zone.There is a blue curtain on the left, and a dark sink on the right.

Black hanger is on the wall, luminous lamps are on the shabby concrete ceiling.