Grout whitener runs about $6 at the local Ace. It comes in a container exactly like sneaker polish, and wastes a bunch. Use an artist's brush instead. After application, drying, and cleanup, let it dry some more and apply grout sealer. Try a salvage yard for tile to match your counters, or find a larger tile in the same color and have it cut to the same size as the old ones. Tile counters give a great, funky, vintage look to a kitchen. Get some eBay vintage kitchen accessories to spice things up, and enjoy the compliments.