Hang on to your hat - recently I re-stained the kitchen grout. Earth-shattering, I know. But it made a huge difference to me, seeing as how I am a little OCD when it comes to cleaning. And you cannot get your kitchen to look really clean if the floor looks dirty. I don't know how we got talked into the putty color that was put in with our brown tile....
I even told the lady at Home Depot I wanted to not have to look down and realize I have a dirty kitchen floor; I wanted brown for camoflage! (our old floor was white) We've scrubbed it and had it steamed clean, but the grout was stained to the point of it looking grubby, and nothing helped. This is one of those projects that stayed on my list for what seemed like forever, but here is what I did: I moved the kitchen chairs out, swept, mopped...sulfamic acid, mopped again, then put Grout Renew on with a toothbrush. Yes, it was tedious. All-day consuming. Made the house smell like vinegar. But look at the grout now (even if the photos aren't the best);
The new color is "Nutmeg", but if I ever re-do it, I'll special order a darker brown color. Even so, I like the way it looks compared to the lighter grout. It's more practical too, and its a sealant in addition to being a stain. Now I just have to remember to take the PineSol bottle out of the kitchen so I am not tempted to use it....you can't use solvent based cleaners on it. Guess it will be hot water and Murphy's Oil Soap for me. But now, when I look down at the floor, I don't stress over it looking filthy!