These are bathrooms I just did a couple of weeks ago. All used a grout a little darker than I usually recommend (Hydroment Delorean Gray), but that's the taste of the homeowner:

This is more the color I recommend for BOTH the subway tile, AND the hex:

Laticrete Silver Shadow:

or Mapei Warm Gray:

I think your ideas sound great. My parents renovated both of their bathrooms about five years ago and I convinced them to use white hex tile; I love the look. They used white grout, and almost immediately it looked incredibly dirty. It kind of ruined the entire look of the floor. I would not advise to use white grout. I'm not sure if the black/white hex would look too old-fashioned, but I personally feel it would look a bit hokey. There is something clean, pure, and classy about white hex and white subway tile. Have you thought about white hex with a very dark gray or black grout? I personally think this looks very nice. It would also pick up the black from the honed granite counter if that is what you plan to go with. I wouldn't worry too much about the grout on the wall and the grout on the floor matching. They are two very distinct planes so I believe distinct grout is perfectly appropriate. www.restorationtile.com has some great images of hex/subway tile installations. Maybe take a peak there for some ideas. As far as wall color is concerned, perhaps a subdued smokey purple would look nice (benjamin moore vintage wine). It would look feminine, yet classy. I wonder if pale blue or straight pink might make this environment that you've worked so hard to make look juvenile. I know it is a bathroom for children, but I'm guessing since it is in a 1920s house, it is probably also used for guests. Hopefully some of this helps and is not just a bunch of distracting jibberish. Good luck!

Newhomeowner2011a are you my secret twin? I'm just finishing a black and white bathroom for my 2yr old and newborn daughters.

We did W&B octagon-dot on the floor, a black vanity and a bianco romano counter (choose a resined slab and it'll be stain-proof and etch-proof). We too did not feel that marble was a good choice for a kids bath, and also we wanted to use the same slab for all three baths we were doing, so worry-free BR it is. The walls are white because all of the design choices were made while I was pregnant and we did not know the gender ahead of time. When #2 came out a girl too, we chose accessories that are black and white flowery with bright pink, blue and green accents. Let me know if you want a few pictures. It's not all the way done yet, but close.

DH talked me into using white grout on the floor and it was a mistake...about 2 days after sealing, one of our cats puked on it and it left a shadow. I wish we used the warm gray that we chose for our master bath's white subways. On that note, I think the warm gray highlights the shape of the subways and recommend it for your tub area too.

As for the black counter, I think it would work fine with a white bath. A few good accessories will make it work without any other permanent black aspects. although, I'd be tempted to do a few black "flowers" like in the picture Bill posted...so cute for girls and totally period appropriate.

Wow - thank you so much for your helpful responses! I just love this website :-)

I've decided to go with the white hex and the Laticrete Silver Shadow grout - I looked online and saw several pictures and I really like it! (is it darker or lighter than the Mapei Warm Gray Bill V? I think they are very close according to this website - http://www.grout-aide.com/colors2.html) I actually really like the black/white example Bill V shared as it doesn't over-do the black flowers but after a bit more thought, I think that the all white hex will give us more options if we decide to change the paint later or the next homeowner has all boys :-) I'll have to save my idea of having black honed granite for our kitchen remodel next summer!

* Side note, this will just be the girls' bathroom - we are currently adding a master upstairs as well and a powder downstairs for guests - you will certainly be seeing many more questions from me as we get closer to making final decisions in both of those spaces as well ;)

Thanks for all the responses re: grout not matching between the two spaces. Bill V, I'm definitely giving consideration to both being the same as you suggest but going to leave that up to my husband to decide. I saw a picture on this forum that has the grout you suggested as their surround and it looks lovely with the chrome!!!

alku05, yes, please share pictures! Does your granite have the garnet speckles? I read online that some of these slabs do and some don't - obviously with any of the paint options I'm looking at the red garnet speckles won't work ;) I also read that this slab resembles marble but without as much worry about staining - certainly something I'm going to look more into!
- On that note, do you think the space will look balanced if I picked a granite like this one (with grey and/or white tones) if we go with all white and just the lighter grey grout?

Thanks to all who responded - if there are any other suggestions or pictures you could share with me, I'm all ears and of course appreciate all the help!

They ARE close in degree of "darkness", just different tones of grey. Sorry-- my navy days showing thru-- but the warm grey is more of a machinery grey, and the Silver Shadow is more of a haze grey. :-)

Our BR does have some garnet speckles, but it's not jewel-grade garnet so they are very subtle, and read more of a dark spot than reddish. I actually think it would be nice with pale pink or pale blue because a lot of what looks taupe in the pictures is a bit of rose quartz, and the gray in it is blue toned. We have parts of the same slab in our gray guest bath and our bluish gray master bath.

Baby is asleep so i took a few pictures of the bathroom for you. Tight space so it's hard to get good pictures, and also it's not done yet- still needs a large black-framed mirror, and wall art to brighten it up a bit.

From the hallway:

From the toilet area:

The tub:

Closeup of counter:

alku05 - thanks for taking the time to snap some pictures for me - your space looks great! Looking forward to checking out some larger slabs of this granite in person! On another note, what color "tan" is the paint in your hallway? :) (it is camel right now and I'm searching for something lighter)

Bill V - thanks for your response :) Another question for you - what color chalk do you recommend? I read that if you do bright white grout then you use bright white chalk - if we use one of the greys you shared pictures of what chalk do you rec'd?

Thanks again for the feedback - I appreciate it!!!

Use a matching caulk from the same manufacturer as the grout, and in the same color. Once dry, it should look just like another grout joint.

The hall is painted Glidden's "Water Chestnut" color matched in SW paint. You can get a paint chip of it at Home Depot. (The online swatch doesn't look like it at all.)

I'm doing my kids bathroom right now with very similar finishes. White subway tile in shower/tub combo and also decided to do it up the wall halfway, white cabinets (BM cloud white) chrome fixtures and hardware, big difference is I've had white tile in bathrooms before and despise cleaning it so I went with black slate with a gray grout. And other difference is I chose paperstone in a black finish for the counters. I've never liked shiny granite and paperstone is softer to the touch and warmer and has almost like a honed quality. I'm also painting the walls a warm grey color (I have an 18 month old boy and 3 year old girl so gender inspecific it is). Here is a picture from a few days ago as the tile is going up. You can see the floor a little too.