I had the baseboard grouted wall color. I used cove base which was installed first so instead of seam at the floor being in the corner, it is on the floor and is grouted like the floor. You will have caulk in that joint. I would recommend wall color for the base.

I would want the finished grout to be a medium gray, light gets dirty no matter how often you clean it. Having said that and from personal experience, I would pick a darker grey and hope when it is done it is at least medium in color. In our previous house we had tile professional laid and grout applied. I picked a medium grey grout, but not sure what happened, the grout was a very very light grey after it dried. Either the installer used too much water or what , not sure. In this house, my DH decided to do a back splash in our bathroom downstairs. We picked a light grey brick tile, and I picked a medium grey grout. We were careful not to use too much water when cleaning the grout off, but again the darker grey color I thought I was getting was a much lighter grey. I dont know what it is about grey grout but be careful.

From my phone I agree that the picture I found online to post of my wallpaper doesn't look navy :-) The wallpaper has a white background with a navy geometric pattern on it. I don't want white in our entry with our weather and little kids :-) We just did a whole house remodel so we are planning on staying here for a long time... if not, the new homeowners can change it given the small size of the room (25 sqft). Odds are given what I've done with navy in the rest of the house, someone that doesn't like the color won't buy our house anyway ;) With the bold wallpaper and big white baseboards, I was loving the idea of a pop with the dark navy floor...

I think I would go for the 2" hex tile. maybe get a couple sample sheets to see how they look in the bathroom first.