Good question - its about the look your after. Gray grout is definitely easier because it won't show all the mould and mildew build up in a shower. White is such a clean, classic look. For your shower, I'd go gray.

i love a light gray grout on the floor, and on the shower floor, but I tend to use a white grout on the walls of the shower.

I would be confident with your choice and do all the same coloured grout - especially in a shower area. If you do both, it could look like a mistake, and the tiler ran out of white or gray grout...

I have a question for you. Is the tile a white white? It looks like it is not a real stark white - a little more off white? I reallly like it.

THanks for all the suggestions. The subway tile (the 2nd photo) is actually a light gray that can have green undertones in certain light. So the floor tile and the subway wall tile are not the same color. We are definitely keeping all the floor grout the same color - my quesiton is really whether it is best to keep the grout consistent on the floors and walls or if it is ok to go lighter on the wall tiles in order to draw attention to the tiles themselves, rather than the grout lines.

Hi Adornan, I would keep the grout the same - if you change it in a shower area, it will bring attention to it. You want the beauty of the tile to be the star and not the grout...