I recently received an order of "light" colored travertine floor
tile. Only this is, it's mostly "medium" to "dark" in color. The
vendor told me that because it's natural stone, it's subject to
"natural variation" in color. I accept this answer, but I'm not too
happy about it.

So what I'd like to know is this: Is there any solution that I can
apply to the tile (hydrogen peroxide, bleach, etc.) that will lighten
its color? Is there a commercial product available? Is there
anything the tile installer can do, perhaps with a certain type of
sealer?

Thanks very much.