Our tile guy used a stain-resistant commercial grade grout by Tek in our shower. It doesn't need sealing because it isn't porous enough (like regular grout) to be susceptible to stains. It costs a little more than regular grout but well worth the additional cost in our opinion.

I would not do white. It sounds like you are having hard water issues that are discoloring the tiles. Short of getting a water softener, you might want to consider doing something different from before. If it only happened once, I'd say it's a fluke, but since it has happened twice, I would try a different route if I were you.

I just wanted to add that if the grout does get dirty you can refresh it with Aquamix Grout Colorant. They sell it in every grout color imaginable. I did it on my kitchen floor and it is a miracle how nice the grout looks now.

I wouldn't do white grout on a shower or bathroom floor. White tile would be fine.

"Fusion Pro" from HD. Antimicrobial, never needs sealing and stains don't set.

I regret using white grout in my bathroom. Its a pain to keep sparkling white. In fact, I am trying to convince my husband to dig the white grout out and replace with gray.

If you have hard water, you can't fight it. NO color of grout is immune, and neither is the tile. I use a pumice stone on mine, and a lot of elbow grease.

We did get a whole house water softener, and it's better, but not perfect.

You can bleach white, but you can't bleach hard water damage.

I am in the process of having a new tile floor in my bathroom now - I bought brown grout. I said something to my installer about it and he said to never, never, NEVER get white grout. I agree. Once burned, twice shy.