Just saw your post and while this is probably too late to help you, your query is coming up on Google so here goes.

I've installed a ton of this stuff in my home. Kitchen, three entries, hallway, and nook. It comes out of the box lighter than most pics, more light grayish, but as soon as you seal it (and you must MUST seal this stuff) it's gonna darken. I could send you pics but I used Aldon's SBS and it took it at least 3 shades darker. Makes the iron and browns show up well but the gray really darkens.

I like my floors a lot. Nice to walk on, nice to look at, very easy to clean although the sealer is more at play there than the slate.

Two tips.

One: You or your installer should use a medium set mortar, not thin set. I really like Laticrete's 220 but (in gray) but it can be hard to find. Much easier to level this stuff with a medium set than with thinset or one of the new enhanced mortars.

Two: Absolutely use a pre grout remover. I highly recommend Aldon's Easy Grout. I did a few tiles w/o it and took an hour to clean. Comes right off with Easy Grout ... put in on pretty thick, a bit more than the instructions allude to.

I would be interested in seeing any pictures you have to post of this slate. I'd like to see how dark it gets once sealed. What do you clean it with? Does it show dust easily? Is it cold in the winter? How does it hold up to pets and farm life? Please post pics if you have time.