Here are a couple more pictures - yes, the dark spots are where the tile is still a little wet. But as you can see the dry parts look terrible.

So you would ask them to regrout?

I really thought I would be getting a grout that would not show so differently when wet (because shower floors tend to stay wet under the shower head).

If they refuse to use the grout you recommended above, what color would you ask them to regrout with? I looked closely at the tile setting and it is not exactly even so a lighter grout would probably show how it is "off."

This work was done on a brand new house and this is the master bathroom and this company did all the tile work throughout (all tile floors and 3 tile bathrooms).

I don't get the impression that these "Professionals" like to be told how to do their job.

They need to remove the grout and re-grout. They used the wrong grout on the walls. Wall grout is Unsanded. Do not settle for a cover up job. They made a mistake and now they are trying to paint it?? Yeah no they will have to redo the grout period!!

Why wouldn't he use the same grout color that was used on the walls? It would have matched perfectly. Did he check with you first? did you select grout colors and he did his own thing? Or did you leave it up to him?

I don't mind the dark grout because it's dark tile. I did the same in my own.

Jana, here is mine. it's black. It dries to a dark charcoal, doesn't change colors when wet. this is a stain resistant grout. Mapei FlexColorCQ. I never had any discolored areas (you absolutely cannot dilute this grout w/excess water during the sponging off period. very little water is necessary. so if they use this grout, have them watch the online video. It's premixed in the container)

I would have them regrout. dig it all out and redo it. if you want to use the same grout, up to you. you might want to switch to a dark gray for less color variation. that grout will have to be sealed throughout it's lifetime. If you want to switch to the Mapei, you could do that to.

they are trying to cover up a bad grouting job. I don't care what they try and tell you, too much water was used on this grout. dark grout is very challenging and must be done correctly. If you want to use the paint option, then get a discount on the tile work.

@ Filipe -Polyblend sanded grout can fit into 1/8" grout joints and larger. From the photos, the grout joints look to be 1/8" - 3/16"... perfect size for sanded grout. Mapei has a sanded grout that can fit into 1/16" grout joints. It depends upon the size of aggregate the manufacturer uses during production stages of the grout.
Wall or not, sanded vs nonsanded grout depends upon the size of the grout joint.

Personally, I feel you need to allow more time for the curing stages. You can seal your grout but it will still darken when you shower. The moisture will evaporate when the shower is not in use and the area will lighten again. And as Beth explained up top, if the installer used too much water when he was cleaning the grout and tile after installation, it can dilute the coloring of the grout causing high/low variation. It's a light grout, this salesman would have guided you towards a darker grout for the wet floor.

I would make sure they used the correct grout to begin with. Sanded grout is always applied to flooring while UNSANDED grout is applied to walls. If you want to have him re-grout, maybe ask for a premixed color to help avoid the color discrepancies you see in the picture. Lastly, seal the grout. We always, always, recommended sealing it at least once a year. Dark color grout needs a bit more care when applying. I do like the color grout you chose for the walls.

What happens when your wall tiles have 3/16" grout joints? Do you use nonsanded grout? I hope not. Nonsanded is made to fit in extremely tight grout joints and it can be installed on the floor or wall. Sanded grout is also versatile and can be installed on either floor or wall. That's a bunch of hockywash to think sanded is only for floor use and nonsanded for wall use...

That is the problem we have offshore tile mfg's making these sheet mosaics with grout lines that are too big for unsanded and too small for sanded. What you have to do is a double pass or pound that grout in tight to avoid it shrinking back and cracking. If your tile person needs to do small batches on a shower pan get another tile person.

You have to let your floor dry to determine if the color is consistent. You can see by the drain it is darker. When a person grouts a floor if they over wash the grout they take out the color.

Let the floor dry. What they can do is use a stiff bristle brush and go over the grout lines what that will do is expose the grout underneath and even out the tone throughout the floor. You will see the grout change as you brush. Obviously do it lightly. Then when you seal it will again help even it out.

That said cementitious grouts will always show darker when wet. Saker grouts show this even more. Another problem is mosaic tiles are hard to clean out all the thinset between the tiles. Id the tile person does not do this those spots will always look darker.

Put a fan in there to dry it out. use a stiff bristle brush across the entire floor. Use a sponge to wipe off the floor. Rinse that sponge constantly as you will be pulling off the grout dust. Let it dry and then seal. It will look 10x's better. There is no reason yet to dig out anything or use any other product. You will expose the true color with brass brush and a little elbow grease. LET IT DRY FIRST!!

Beth is correct that Mapei grout does eliminate any color issues but also has its drawbacks on a floor.