I wouldn't think that a commercially pressed and fired tile with a low water absorption rating could absorb enough moisture to have it shadow through the glaze. Especially on a somewhat short "come and go" cycle.

A more absorptive handmade and kiln fired tile? It's possible.

Natural stone tiles? As you wrote, for sure they could shadow moisture.

I have seen cracks in the glaze that have admitted moisture in spots behind the glaze. I've even seen crackle glaze that was moldy and discolored in the "crackles".

Edit to fix speling misteaks.

This post was edited by mongoct on Thu, Feb 27, 14 at 8:33

It doesn't matter which tile you use, water should NEVER be able to get BEHIND the tile. It's true that some tile absorbs more water, but that tile has to be well sealed and definitely seal the grout.
You also have to have make sure there is a waterproof membrane behind the tile. Drywall in a wet area is an absolute no-no. You should use a cement board with the waterproof membrane over.

Four tile setters I have recently met told me that ceramic and porcelain tile that is not handmade will not absorb water and discolor.

Can't water seep through even sealed grout to get behind the tile? I've been told us is why we have waterproofing on the wall behind any tile.