I've used us sanded grout and never had a problem.

I've posted in "dilema" section but I think it belongs here since I just found someone's floor with the exact tile I just bought - I need advice on which grout is best to use for this Serso Mahogany tiles - Lowes recommended unsanded TEC Power Grout 550 - but I read some very bad reviews on this product. Many thanks!

Guest bathroom shower surround, glossy white tiles, "regular" TEC grout, 2008 I think. MB and hall bathroom tub surrounds, glossy white tiles, TEC XT grout, 2011. No issues. The XT grout doesn't require sealing, but can be, using a solvent based sealer. We have moderately hard water. We wipe down the tub surrounds with a microfiber cloth after showering (to prevent water spots on the glossy tile). I clean the bathrooms pretty much weekly. I spray the tub surrounds with 7th Generation disinfecting bathroom cleaner spray. Let sit a few minutes, and wipe dry with a microfiber cloth. Tile and grout look as they did when first installed.

I have a gray-blue ceramic tile, definitely cool colors. Light to mid gray. The blue came about because I wanted cool gray with no brown in it, and most gray tiles include brown or have brown undertones (warm). The blue definitely comes through in sunlight, not so much otherwise. Walls are a slightly cool white. I understand it's best to stick with warm or cool colors, not mix them, and surely a warm gray would stand out. My contractor wants to use Tec Power Grout (tho opinions on Houzz seem mixed). The gray samples I saw in Power Grout all looked like warm grays. It's possible that the dealer may not have had samples of some newer grays - ? Would those who have used a gray from this line please comment? Maybe some are at least more neutral?