I just came across this thread, and don't know if anyone is still reading, but wanted to write, because I just put up my backsplash (in a new white shaker style kitchen). Everyone who sold the white subways said to use white for the grout. But most people in Gardenweb were saying to use gray? I didn't end up buying at home depot, but a guy there said it best. He said that the "authentic" color of grout used with subway tiles at the beginning of the century was always white. I told him mine looked creamy to me, and he said "If the tile reads white, at all, when you look at them, use "bright white". When you see subway tiles in a movie and the grout looks gray, that is done to make them look very old and that the grout has gotten dirty/discolored after many years. He said it is was in the 1980's that gray or black grout started to be used with a white tile. The brick pattern doesn't dissapear with white grout. You can still see the brick pattern under lighting because the tiles aren't totally flat. It's a cleaner look with white and authentic to the early century rather than the 80's. The original subway tile did not have beveled edges. This allowed a smooth surface as opposed to the modern tile which really defines separation in the installation.

Thanks J Hack.......it has both gray and brown in it with a strong lean to earthtones, which I think will allow me some flexibility when making color changes to the room. I was thinking of using a light grout color, but wondered if it would look okay between the accent or be to stark.

I'd do black floor, grey shower. A white or lighter grout WILL end up looking black'ish eventually in those high traffic areas. I can't tell you how many houses I looked at that had two toned grout; the high traffic areas had dark brown while the edges of the rooms would be light tan. You won't have to get down on your hands and knees with a toothbrush trying to clean the white/light grout saving your knees and back for years to come.

Nidnay and chispa This may happen in the future, but this bathroom was completed two weeks ago and I noticed this greying in a small area before the bathroom was ever used Thank you both for your comments this is what I am not understanding…. The greying is only in a small area of the shower. The walk-in shower does not have this greying anywhere else or on the rest of the floor (I have wet the entire floor at some point) I have a black floor and black grout ( not epoxy gout) in a powder room I had renovation 11 months ago. I clean this floor regularly and I don’t see any efflorescence happening. I do know when the tiler requested me to fill her Home Depot bucket with water ( multiple times ) I can more understand what Millworkman said.