I haven't done it yet, but my plan is a light gray grout. I googled a lot and searched forums and some people were noting that they used white and it was getting stained. not sure how true or isolated it is. but we're doing the light gray to hopefully fix this.

Thank you for the responses. You both echoed my thoughts on the silver/gray tones. And, pacific flights- your shower is gorgeous!

Here is our gray........

We had white 4x4 ceramic tiles with white grout before in our bath. HATED them! You could never keep the grout clean! I vote for grey also.

I thought I wanted a silver/gray grout, but at the very last minute, I changed my mind and went with white. I'm happy with my decision.

We went with traditional white grout and it has not been a problem to keep it clean. It has been sealed and we wipe it down after our showers. It looks great in our black and white bathroom.

another vote for white

If you use a quality grout, upkeep shouldn't be a problem. I had white grout on the walls as well as the floor in my last house, and never had a problem with it. I am not in any way a fastidious housekeeper, and we didn't even wipe down the walls after use. After 15 years the grout was still white.

Testimonials aside, there is no doubt that white shows dirt/grime/whatever more than gray.

Beyond that, it is just a personal preference of what you want it to look like. Gray grout is a much more traditional choice than white. If you are going for a vintage look, that would be my choice. On the flip side, if you are going to more a more "clean line" modern style, then I'd go with white.

You can get color samples from your tile dealer, contractor or go to the large box stores. They have a smaller selection.
Your tile installer can color your grout based on the samples you see.

Also - consider your water. We did a renovation about three years ago in our recently purchased house, with white subways and white grout, and didn't realize our water has some rust in it. After putting in a water filtration system, we still have yellow-y grout where the water hits. It drives me insane.

We used white grout with white tiles in all our bathrooms, since we prefer the look of the grout blending in with the tile. Would do it this way again, but I do think the grey grout looks very nice in the bathrooms posted above.

we did white with the subway tiles in the shower. The white and white just makes it look so clean. It's been 1 year and we have not had trouble keeping it clean. We did grey with the carrera marble on the floor. That looks great too. see my pics

I'm glad Brian asked this. I hadn't even thought about grout color yet. Love seeing all these examples.

Does anyone know of a color closest to Mapai #103 Cobblestone? Maybe in a Custom Build or Polyblend?? I can't even find Cobblestone...UGGGHH! I am buying in a rural area where my choices are Custom or Polyblend.