I vote for grey - not a dark grey perhaps. Not only do I think it would look better, but with my history with grout - white! yikes!

I think a light gray would look nice and tie in with your countertops.

Light grey grout is my vote.

white all the way!

Keep it Clean looks great!

We had the very same dilemma but ended up going with medium gray grout and I really do love it. It's not busy at all and I'm picky. I don't see any uneven grout lines at all. In the end, we are very happy with the outcome.

I vote for white unless you want the grout to become a design element. I don't think you need that. Is that what you want? Good luck to you, hope it all comes out exactly like you've always dreamed!

White.

I would go with white! You can always add color to the kitchen in other ways!

White for the new section to match the white on the old section.

Another vote for white.

White!

I always like to use a very light, powdery, silver gray. My favorite is a color by Bostik (Hydroment) called Silver Bullet. Another company makes one that is almost identical called Silver Shadow. Tec Silverado will work but it is a bit darker.

That being said, white can work, too. However, maintenance is much harder because white shows EVERYTHING. It never stays white. If it were my kitchen, I would use Silver Bullet with no second thoughts.

acm makes a good point. I did not notice that you were only grouting the first course. Because the rest of the backsplash is white, it only makes sense to finish with white. Seal it after the grout dries. It will make cleaning easier.

White!

I like the white!

I like white!

Aesthetically, I usually suggest white grout with white subway to allow the countertop stone to stand out. However, functionally, given that it will be susceptible to both grease from the stove, and wiping residue when cleaning the top, I always offer a light grey as an attractive option...

White is probably going to work best.

I vote for a light gray.

I did a light color with the small hexagon white tiles. None of them pop. I was going to do darker but the tile guys convinced me that was bad. No way. I'm now trying to change it to a medium gray to match the stainless steel color in my kitchen. I like the tiles to pop. It looks cool. Even black can be very cool. I've seen lot of designers do that.