I'm putting tile in a frameless shower. The bathroom already has a medium gray Saltillo tile with dark gray grout. The shower wall tile will be a very light gray with cream and medium gray swirls. The floor and trim inset around shower walls will be a dark pebble mosaic. Should I use dark gray grout on the walls ( to match that on the floors) and a light gray or cream grout on all the pebble mosaic areas. I'm afraid the dark grout on the pebbles will make the mosaic look too dark and the pattern will disappear. Is that too busy? The countertop that's already in the room is a cultured marble of similar colors as the shower wall tiles.