For the wood-look floors try to find as perfect a match to the tile color as possible, so that you hardly notice there’s grout there. You don’t want to call attention to the “grid lines.”
For the shower, be sure you really want natural marble on the shower floor. Porcelain marble-lookalike tile are less maintenance. Personally, I think it’ll look weird to have dark grout on the shower walls and lighter grout on the floor (unless they are very very clise). I’d pick one color grout for the whole shower. I prefer a very light gray with white tile. We used Mapei “frost.” If you like darker grout, okay, but match the wall and floor. Have your tile pro create sample boards for you before finalizing your decision. That is standard so that people can choose the grout after tile is up, using a grouted sample board.
Read up on and pay attention to waterproofing: proper slope to drain, waterproofed walls, floor, curb. It all must tie together as one waterproofed system before the first tile is installed. You could actually shower in it without tile or grout; that’s how waterproof it must be. Tile and grout are not waterproof; that’s just what you see on the outside. Be there for the flood test, when they set it up, and when they measure and pull the plug (and don’t let anyone in without you there during the flood test or they could add water to it to cover up a leak; ask me how I know that!).
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Tile ADVICE/water proofing shower
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