I think you've done a nice job arranging the tile, which is really pretty!

As for grout, I might shy away from white in a kitchen if it's going to be near cooking or a heavy food prep area. Laticrete has a color called light pewter that might be a good fit with the more gold-brown veins in your tile. It's a taupe grey that would hide stains. Sauterne (a beige) looks like a possibility, but might be too pinkish.

You can order sample sticks of grout from Laticrete and get them in the mail in short order. Go to their web site. They are free. I ordered several of each color I wanted to look at.

Beautiful tile. and as KMCG states nicely arranged.

I have Laticrete samples of Silver Shadow and it is a cool light gray. When I put a sample of Smoke Grey next to it, the Smoke G. looks warmer but has a slight rose color to it. Not so noticeable by itself, but in relationship to the other color, it presented itself. It is very helpful to have an assortment to look at, not only with your tile but compared to each other. Some of the under colors are hard to detect but will clash with the tile if not chosen carefully.

If you are at all challenged with color, have someone help with these subtile differences. I know some men struggle with seeing these differences. They may not be diagnosed with color blindness but there seems to be some people who have difficulty seeing the subtile greens and reds etc, on a milder level. Men are more likely to have color blindness than women because it is related to recessive genes on the X chromosome.

What do you think about using the leftover box of TEC dove gray I have from the bathroom remodel? The bathroom calacatta gold is more gray and the kitchen is more brown-gray in the veining. See below.

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If in doubt, make up a tile board and grout it. Or get sample sticks :)

I would be afraid that the colors wouldn't mix well with the warmth of the yellow undertones of the kitchen. Your Bath is much cooler.

I am using Silver Shadow for my white field tile with marble accent listello that has a cool and warm mix in the mosaic. I am using the paint color in the upper left corner. Not the lower paint sample that reads green.
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Tile board with white tile and Silver Shadow in the left set. Top right is 2x4 marble with 50% Silver S. and 50% Platinum as well as straight Silver S. note that the grout isn't totally dry yet and has that halo effect. The black slate has 1 part Silver Shadow and 2 parts Platinum as well as a 50/50 mix. I also sampled Raven and mixed with Silver Shadow in varying degrees with the slate. The cross bar that the grout line makes on the black slate is something that I thought would work but when I poured the dry portion into the mixing container it looked rosey. And you can still see the rosey color in this picture though it is very subtle. Thats why is is so tricky. Several weeks ago someone posted a gray grout color that read lavender with her white hex ceramic. She was concerned that over the entire floor it would stand out. The Silver Shadow and the Platinum are perfect for me in my Bath. These 2 grouts look blue to me as I work with the samples. The Raven does too but just a very dark variant.
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But I wouldn't wouldn't use Silver Shadow with my kitchen marble that has a lot of gold undertones.

I used a grout that I found at The Tile Shop called Natural (ever so slight green undertones) and I mixed it with white to tone it down. My walls are a green and I have cherry wood so green and orange.

That seems like far to much effort, and I am thoroughly impressed that you would dedicate that much time to it. I don't have that much time (or enough extra tile) to deal with that. I was only able to buy 44.5 square feet because it was a close out at a local marble yard I go to and I got a great deal on it (I always seem to find great deals on calacatta gold, I know, I know).

Here are the options using TEC's AccuColor Grout and Caulk Color Selector strips (which came from my local tile retailer):

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From top to bottom; Silverado, Dove Gray, Ivory, Mist, and Pearl. I kind of like the Dove Gray (which I happen to have a full container of leftover) and the Pearl.

Thanks for posting this picture. I chose my favorites before I read your full post (so not to be swayed). I picked Dove Gray and Pearl too.

The top one looks like it has a rosey cast.

2nd, matches with the grayer veins in you image.

3rd, might work but a little bright for my taste.

4th, might work but a bit too dark maybe, almost looks like a darkened #2. Or it might have a bit more yellow in it as I see from your picture.

Last, I like the toned down color and goes well with the stone I think.

What sized grout line are you going with?

I like the top one, second one, and last one. I'm a fan of using what you have, and I think the dove grey would be great.

Enduring - that's remarkable tenacity in your grout testing!