I don't know if marble can turn a different shade, but I do notice in your pictures, that the first image shows that the colors go pretty well with the countertop, but in the second 2 images, I see the blue tone you see.

Which leads to me to question your lighting. There are so many threads about kitchen lighting making white cabinets look yellow, and counters that look completely different once installed.

I believe that your issue MAY be the lighting. Are all your bulbs (undercounter, overhead, pendant, everything) the proper daylight CFM?

Here's one thread, so you can see you're not alone.

https://www.houzz.com/discussions/grey-countertops-in-kitchen-look-purple-in-different-light-dsvw-vd~4865325

Let me keep looking for some of those other threads, where specific CFM of daylight bulbs are recommended.

https://www.houzz.com/discussions/white-cabinets-look-yellow-dsvw-vd~5224453?n=83

The same thing happened to me. I was distraught! But was assured that the tiles would lighten up once they completely dried and they did. White marble is very porous, just give it some time. By the way, you have a beautiful kitchen.

Sorry Tiffany but I just searched and couldnt find it but it was quite a lot grayer. I had done this before but just checked with a spare tile and it looks exactly the same as the tiles fitted on my wall.

I just read where here on Houzz where someone else suggested waiting at least five weeks! But I don’t remember it taking that long. I think I noticed a difference in the first week or two. But maybe it takes that long to completely dry and turn 100%. Forgive me if you already said this but I assume your tiler used white thin set not black?

By the way, the same thread said sealing shouldn’t make a difference unless you use an enhancer. Sealers apparently allow the gasses to escape when drying out.

I know!! Keep us posted if you can. How long has it been so far?

The same just happened to my newly installed floor and I am sick, although the vender recommended waiting a few weeks before doing anything rash. Note the loose, uninstalled mosaic sheet on top of the installed tile in the picture.

No offense but the backsplash and countertop combination doesn't work well for me. Not only do the colors clash but the patterns do as well.

That’s a difficult combination to pull off.

Not sure what you are eyeing, but no backsplash here, only a bathroom floor and shower wall. Regardless, to each her own.

s1eph…I’m about to put that same flooring in a powder room. Has your bathroom floor lightened yet? Your bathroom looks nicely done. On a side note, I’m pretty sure Norwood and Kate were most likely referring to the OP.

Yes, the marble lightened somewhat; some is still light gray. A sound abatement layer had to be installed under it because of condo covenants, which slowed drying and lightening.
I have learned to check the grade of the marble before purchasing.

That is quite a change. The OP had two different tiles she was showing...so wasn't really sure their original desire. Dark or light your floor is beautiful!!!