I'd love to chime in, but I'm having trouble getting a read on the color of that tile. In the photo, half of it is whited out with glare, and the other half looks to be very dark grey with maybe a hint of blue? Maybe my monitor is bad. But if it's not just me, you might not be getting much advice because others are having similar trouble getting a clear impression of what the tile looks like.

Do you have any more/better images of it? Could you take a photo of a few sample tiles laid out together, if you have any?

Wow, so in the top photo, that is 2 of the same tile sitting right next to each other (1 dark grey, 1 almost black), and another in the second photo, catching the light and looking like a light grey? That is definitely a tough grout color choice! Forget advice, you need a lot of luck and perhaps divine intervention in order to get this choice right! :)

If I were you, I'd focus on grey grout colors that are in the middle of your tile's most common range (not the lightest that your tile looks when it picks up the light and shines, and not the darkest either, but closest to the color that you think the majority of the tile will look, when you're standing at a decent distance from it).

Sorry that I can't be more specific. If you post some grout samples that you are choosing between, that might help, too.

You do know that those translucent tiles will look very different once installed and grouted, right? Also having the iridescent finish can really affect the look depending on where the tiles are located and the light they reflect. Some of the iridescent effect will show up as a purple-ish color.

Have you seen large sample boards of these tiles?

Also order extra tile as some of the glass tiles will have imperfections that are within the variation specifications, but did not look right to me. For example a big air bubble in a tile. I got extra so I could discard the ones with major "imperfections". I used tiles from Oceanside Glass tile in 3 bathrooms so I've learnt from those projects!

Beth, 2 of the samples she showed are translucent, on one you can even see the label behind. In addition, imperfections/voids in the thinset will also show through those translucent tiles. Just giving her an FYI on the samples she showed us, which might also help anyone else considering some of these glass tiles.

I would do grout in the closest color to the tile, erring on the light side.

I might look at grout the same color as your walls are? or even as the cabinets are. Just depends on the scale of the tile to the room. If the pieces are larger, you should probably do as crl recommends.

grout is for tiles. you don't match your grout to the wall color or the countertop. you match it to the tiles.

mrswaves,,,pick a color that matches your tile. either go lighter or darker, depending on the look you want. if you pick a warm tone, it's going to clash w/the blue gray of the actual tile. you can also use a white like Quartz or bright white, if you prefer and on Mapei, Frost,,,Avalanche is the whitest white on the market.

I’d personally pick a grout color that is matched with the tiles.... or as close as possible. The counter is gorgeous by the way and has a lot going on, which I LOVE. I think if you contrast too much on the grout, it might look too busy in the kitchen.

Grout color choose white or a color close to the tile to blend the lines into the background to keep the focus on the tiles. I prefer this method.

White grout with grey

Light Grey grout with grey

When the grout is darker than the tiles, the grout lines come to the foreground & become the focal point. This can become visually too busy if not planning for it.

Kitchen photo examples of grout with lighter or close color grout.

Darker grout than tile, with a solid color countertop only suggested.

The lines are obvious & was planned to be part of the focal point

Because your slab has many flowing lines, I highly suggest a simple backsplash with a lighter grout than tile or white.

As for irredsecent tiles, they are gorgeous in a showroom. Each tile is mesmerizing on its own. Like jewelry.

They are more of a challenge to use as a backsplash, because they change color & reflect colors & light shapes onto the surroundings.

Check out the reflections in the countertop

Sometimes it turns out gorgeous, but sometimes the light reflecting may be too much.

If want to do an irredsecent backsplash, do a whole sample board with grout & put it under cabinets. See it in daytime & night lighting before finalizing that decision.

It may be a winner or it may be determined decorative irredsecent items & jewelry instead.

That's the best order to do it, Mrs waves .

Backsplash & hardware is like the jewelry of the kitchen.

Kind of like getting dress to go out, the jewelry is last to accent the whole look ;)