Summarize the following:
Open a window or turn on a fan. Keep doors open. You don't want to be in a confined space with bleach. You don't want your skin to come into direct contact with the bleach. Bleach can cause skin burns. Mix one cup (.23 L) of bleach with three cups (.7 L) of water and one teaspoon of dishwashing detergent. Mix it in a bucket that you can dip your brush in. Bleach is a powerful cleaner, but you shouldn't use it on colored grout, because it can cause the color to fade. Dunk a soft-bristle brush into the bleach. Then, rub the grout in a circular motion. Use a clean wet sponge to wipe down the surface, removing the bleach. You do not want the bleach to sit on the surface indefinitely.
Ventilate the room. Put on gloves. Make a bleach solution. Use the bleach solution and brush to clean the grout. Rinse the bleach out with a clean, wet sponge.