The side half walls and floor are Calcutta look porcelain.
The two end walls are glass.
We are using white Thassos marble as the door and shower thresholds.

The vanity top which came with the vanity is Carrara marble. The grey in it is a good match to the Calcutta - but the movement is completely different as is the white.

I initially thought it definitely wouldn't work, but now I'm not so sure. It looks like it is different enough that it could work maybe?

Here's the floor.

No one else has any input??

Here's a (not very good) pic of the vanity top.

It's hard to tell it they work or not. In the photos, the vanity seems so veiny as to be bordering on solid grey (not a bad thing--I like it too). The colors don't work in the photos, but if they do in real life, I think you can do this.

Will there be a backsplash or any of the porcelain or calacatta closer than the floor?

Yes, the porcelain calcutta goes up the wall to 42" so right next to the vanity top.

I think we're going to have to eye ball it. Maybe when the walls are tiled we can stand the vanity in the bathroom and see how it looks with the top. If it doesn't work then we'll have to scramble to find an alternative.

I have a bathroom with porcelain carrara look tile and actual carrara marble counter. The porcelain veins are gray but don't look exactly like the counter's veins. The counter also has more gray in the background than the very white tiles. I love it.

Personally, no I would not mix Calcutta look tile with carrera marble.
I would use real Calcutta for your counter tops. Calcutta is much whiter with warmer tones in the veining while carrerra is much greyer.

We mixed carrera look tiles with real carrera counters. I was nervous about it but it looks great.

Sell the countertop or use it elsewhere in the house.