The best part about white subway tiles is that if you want to keep the look classic you can simply use a matching grout.
White subway tile with dark gray grout.
I semi remodeled my kitchen with long white subway tile and mid dark grey grout and i love.
Many people prefer using white grout with white tiles to make the walls look flawless and united.
But before you name it the best solution for your bathroom thinks about a different approach.
In the photo below notice how pronounced the octagon tiles appear with dark grout.
The flexibility of grout color for white subway tile backsplash is pretty exquisite and if you crave a lighter space white grout is a great starting point.
Well appointed gray kitchen features glazed white subway backsplash tiles finished with dark gray grout and framing a stainless steel kitchen hood flanked by black windows mounted above gray shaker cabinets accented with satin nickel pulls and gray granite counters located on either side of a stainless steel oven range placed on oak wood floors.
Contrast grey grout with white tiles looks wonderful especially if you decided to use subway tiles in your shower area.
In the bathtub i continued with the same light grey grout with white subway tile.
Since i did an inset cubby with the same penny hex the grey seemed like the best option.
Had i been able to do white with white i would have loved the look you chose.
I do love the slight contrast but would have been happy with white white too.
Even with a simple subway tile pattern going dark with your grout will.