Grout in floor or counter top tile can be changed to a different color. This is usually done when the tile is first installed. A dye or coloring is added to the wet grout, and the color becomes defined as the grout dries and sets. Grout color can also be changed after the tile has been installed and the grout has dried. This is done by applying a "colorant." Another method, though unconventional, is to use wood stain to change your grout's color.
Things You'll Need
Trisodium phosphate (TSP)
Sweep off the floor or counter top with a broom and dustpan, removing the surface dust and dirt.
Pour one part trisodium phosphate (TS) in a bucket, and add four parts warm or hot water.
Thoroughly clean the tile, concentrating on the grout, using the mixture and a scrub brush. Rinse clean with plain water, and dry with a hair dryer.
Carefully apply wood stain directly to the grout using a sponge brush. Do not brush over the tile itself or it will be stained as well. It will be difficult to remove the stain from the tile, so apply it slowly and with a steady hand.
Allow the wood stain to dry into the grout according to the manufacturer's suggested drying time.
Coat the grout with an impregnator using a clean sponge brush once the wood stain has completely dried and set into the grout. Let the impregnator penetrate into the grout to help protect the new coloring.
Apply a coat of grout sealant with a clean, unused sponge brush, and allow it to dry as long as suggested by the manufacturer.
If the grout is not as dark as you want after applying the wood stain, apply more coats until the desired shade is reached. Add the impregnator and sealant.