Prepare the area for carpet color repair by removing all furniture from the room or space. Cut plastic sheeting into strips measuring approximately two feet. Attach those plastic strips to the base of the wall using painter's tape. This protects the walls from discoloration caused by the new dye kit.
Vacuum the room or area to ensure a better dye job. Pass the vacuum over the carpet numerous times to remove all dust, dirt and other debris from deep within the fibers.
Mix the contents of the dye kit with water according to package directions, as directions vary according to the type of dye you use. Some dyes may come in liquid form and require water dilution, while other types may be in the form of powder.
Pour the mixture into a spray bottle and use the spray bottle to administer the darker dye onto the entire surface of the carpet. Work the dye down into the carpet fibers with a scrub brush, working with one small area at a time and working your way around the room toward the exit.
Allow the dye to dry for at least two days, keeping the room free of humidity to promote thorough drying. Run a wet vac over the carpet to remove any remaining wet spots on the carpet and to help prevent the dye from transferring onto your feet and clothing. Return all furniture to the area and remove the plastic sheeting from the walls.
Locate all lighter spots in the carpet and remove furniture and area rugs from these locations. To spot repair stains lighter than the carpet's original color, you do not need to remove all furniture from the area or protect the walls.
Mix the dye kit solution with water, according to package directions. Place the mixture in a bowl or sealable container, as desired.
Squeeze a dropper or turkey baster full of the dye solution. Squeeze the dye into the lighter spots of the carpet while pressing the end of the dropper or baster into the carpet.
Rub the dye into the light spots with a rag. Add more drops of the dye solution after a few seconds of rubbing. Apply more drops only in areas that continue to appear lighter than the carpet's original color. Repeat this process of applying dye and rubbing it in until the light spots disappear completely.
Run a wet vac over the repaired area to remove residues of the carpet dye. After this, you may notice you need to apply more dye and repeat this step a second or third time.