i have ceramic tile on my breezeway between the garage and house-only about 8 feet or less. i have to say, :down i hate it. it's slick even with a light rain, let alone snow, etc. its cheap and such, but i don't see it as the last surface that will be on this floor.
that said, i think it'd be WAY too slippery to put under my car when it rains, etc.
as for grout, i would go with black to begin with to avoid the disheartening when it does turn black and you put down white.
wouldn't happen in my house. not ceramic at least.