We have seen a similar issue in the past. The problem occurred when the porcelain tile on the floor did not have 100% contact with the tile adhesive, this caused water to seep down though the grout join and hold in pockets under the tile in the areas where there was no direct contact. The water being trapped in the pockets under the tile does not evaporate and can leave the tiles looking stained. If this is the case with your floor tiles the bottom row of carrara marble tiles are simply acting like a sponge drawing water up. To fix the problem we would suggest that the bottom row of carrara marble and the porcelain tiles on the shower floor need to be removed and relayed ensuring full adhesive coverage. Unfortunately this may compromise your under tile heating and waterproof membrane. Proceed with caution.

I see what you mean, however marble is a classic material that wont easily date if you select a quality tile. What you accessorize the tile with, like tapware is more likely to date but is more easily replaceable. I don't see black tapware going anywhere soon however stay away from copper

Love the sense of movement in the veining in the noble grey, which makes it very like marble (but a more grey look overall, which I like). I find the London Grey has a little too much brown, and the Frosty Carrina a little wishy-washy. But it is of course a very personal choice! Have you also looked at calacatta nuvo and statuario maximus? Beautiful alternatives to marble, but unfortunately in Caesarstone's top price category like noble grey! Here's a pic of noble grey in action: and my current favourite, statuario maximus (from the Caesarstone website):

Haresh, I don't know what country the original poster was talking about, but this is the Australian website, and any answers to your question would probably need to know the city too. It's best to start your own question instead of adding it to a very old thread. If you need to, you can change the website country at the bottom of the screen. If you are in Australia, think about what suits the climate where you are and not just what you are used to. I can understand what the original poster said about wanting marble. However I have seen increasing numbers of sales listings in my city with marble throughout the house including bedrooms and I feel sad because although it is obviously a habitual cultural choice it can affect resale in this particular climate. I thought I'd talk about that because I just saw another listing and straighaway I thought brr, we're going into autumn and that's so cold in bedrooms. Even a nice timber or laminate is better if you want a hard floor. If you are in the same situation as the original poster with "termite and humidity problems in the country [they] are living" please disregard.