Well, I'll throw out another wild one. I'm looking at those joints and they look wider than 1/8". And you said he used unsanded grout? And it appears this guy like to water his grout...I'm almost thinking that if he did a lousy job the first time around, he had problems with the unsanded shrinking during the curing. Especially if he likes water. Maybe a little flaking, a little cracking, a few pinholes opening up. Then he came back on the subsequent visit and grouted again over the existing grout to hide and fill in the blemishes. But that's just too crazy for me to speculate like that. I'm almost tempted to recommend a few ideas, mainly try a Q-tip dipped in bleach to see if the dark stuff low on the wall isn't mildew, and try a bit of an acid, even mild vinegar, on the white stuff down low on the wall to see if the white stuff is efflorescence that the acid will dissolve away. I keep coming back to your first photo: In the vertical wall-wall corner joint that is grouted, the right part of the grout joint looks like the original quartz color. the white stripe on the left part of the grout joint, as well as the white in the horizontal grout lines above the first course of tile, looks like efflorescence. The dark along the tub looks like mildew or moisture. But if the light and dark have been there forever, both efflorescence and mildew take a while to form. If your water has heavy minerals or it's heavily chlorinated, that might be a player. If is he used old bags of grout that were past their shelf life that could be an issue too. Or a contaminated mixing bucket. Or... But as you can tell, I'm just scratching my head and guessing. Does the white grout have a different texture? If you scrape the white with a fingernail, does it powder off? If it does come off, is there any of the true "quartz color" underneath it? Have you tried cleaning this grout at all? Like in my first post, I just keep leaning towards the idea that too much water was used. When I first looked at the photos of the upper walls, they looked like areas of good grout with a few blotchy dark streaks. Now I look at them and see the uniform light color being almost all efflorescence, or I'm seeing grout that has had the surface cream/pigment washed away, and the "dark blotchy areas" are actually the proper quartz color! I'd love to see this shower with my own eyes to figure it out. I probably have to take my son down to William and Mary for a college visit later this month. Bill, how about a road trip? A few crab cakes, catch a lacrosse game while we're down there, we can check out this shower all while taking my son for a college visit? Too bad the Orioles are going to be at Fenway instead of the other way around. Road trip!!! Seriously though, have you tried cleaning the grout with anything? A neutral pH cleaner and a bit of elbow...

Thank you Bill. The Laticrete grout color our tile contractor is wanting to use is the "Marble Beige". That color is close to the darkest color in the tile. But there's not that much of that color so I'm afraid it would really stand out. I'm leaning toward blending with the "Sauterne". Everything else is either too brown or gray. Good to know we won't have discoloration or mold issues. Any recommendation on a cleaning product for our travertine? The travertine will be in our shower, knee walls and bathroom floor. He wants to wrap the knee walls completely with the tile instead of it just being in the shower and top of the knee wall. The knee walls are 41" high on each end of the vanity. Do you think this will look good? My plan is for possibly a very light quartz countertop on the espresso vanity. It's hard for me to envision.

Thanks again Bill. In my second post I should have said that when I clean the shower and wet the tiles, the grout turns dark again, but it's only temporary. Tomorrow I'll call the water department and find out about chlorine. I'll also point out the grout issue to the builder and see what he says. I suppose I could "water" the top part of the shower until the grout coloring evens out but the grout that is underneath the clear silicone caulking is still very dark in comparison. And the shower grout (or the lower part anyway) is much lighter than the grout on the sink vanity. Thanks, as always, for all your help Bill!

Even later in this post and my problems continue. My question relates back to grout not being waterproof and it is expected that moisture will inevitably be behind the tile but not going past the kerdi. Above "Every grout manufacturer will tell you their grout is NOT waterproof. Tile is not waterproof. Sealer adds some measure of stain protection but is not waterproof either. Waterproofing is achieved by a variety of approved methods which fall into 2 categories; 1- Surface applied membranes such as kerdi, Hydroban, AquaDefense, Hydrobarrier, Nobleseal, Dalseal, Kerdi board and its competitor foam board from USG. 2- Subsurface membranes such as the classic vinyl liner WITH a moisture barrier behind cement board such as tar paper or sheet plastic. As a member of the National Tile Contractors Association, I can easily attest to the above information. But it's your shower and your money and you get to decide what you want to do." I have Kerdi board behind the tile so it is waterproof but the tiles continue to gray. I may need to redo the shower surround with different tile.