Is your tile on site yet? We just went through a rough patch with another member here, whose tile didn't match the sample she selected, and she didn't discover that until after it was installed. Examine your tile before it gets mortared in, each and every one, for color and defects. Reject any or all before it goes in. Consider micro-managing its installation, so you can keep an eye on things: make sure all grout lines and edges and corners are to your liking before and after the grout goes in. Make sure any spillovers are perfectly level, etc. Maybe the tile guy won't appreciate you breathing down his neck, so be prepared with some goodies and sodas to keep him happy and on your side. Either way, it's better for him to make corrections before the mortar dries, as opposed to ripping it out and doing it all over...