I'd use this color if I were trying to draw attention to the tiles. If not, I'd probably go a couple shades lighter.

I think this seems dark as well.

Is it dry? It seems much too dark to me. I like grout to fade away not emphasize the tile lines. I also think it may clash with your yellowish parts of your tile . . .

I used to lay ceramic and marble tile floors. The grout color depends on the application (where the floor is located) and the effect that you want to achieve. If the floor will get lots of traffic i.e. hallways, bathrooms etc. you tend to use darker grouts since no matter what you do the grout will become dirty and dark over time. In areas where the traffic is fairly light you tend to use grout colors closer to the color of the tile, this way you avoid the obvious grid pattern. However if your tiles are laid in a nice pattern and you'd like to emphasize it you definitely need to use a contrasting grout color.
I hope this helps

It looks almost black in the photo?

I think I'd err on the side of being lighter instead of darker.

I'd go lighter as well - not sure if it is my computer, but it looks really dark. Have you tried Laticrete's Silver Shadow? I used it in my guest bath and it worked perfectly with carrara basketweave. It has just enough gray to emphasize the gray in the tiles. If you do a search you'll find a couple threads with photos.

Here's Silver Shadow with carrara:

silver shadow looks gorgeous. thanks for posting the photo of it on your beautiful tile, pipdog.

i'm not sure if the grout was wet or dry, but i'll as the tile guy.

thanks, everyone.

Very nice pattern! If I were still laying tiles I would suggest this pattern to someone at least I would keep it in mind. You see how contrasting darker grout creates an illusion of a weaving pattern. Very nice!

I think it's still wet, as DD2 used this in her MBath and it's not this dark. I've attached a picture of Delorean Gray dried.

Tile guy said he did it on Saturday and it should be dry. Would platinum or oyster gray be better?

I used TEC dove gray, and it's a little lighter (and more taupish-gray-green) than delorean or silver shadow. If you look for my threads, you'll see pictures.

If you're using Custom, yes, Platinum would work MUCH better. From mapei, Warm Gray, and from Laticrete, as someone already posted, Silver Shadow. They'll blend into the veins of the stone much better