Pour the grout powder into a bucket or bowl.
Add dry colorants to the bowl as desired. Grout can be dyed with a wide variety of substances, ranging from colored powders to liquids. Herbs, glitter, spices and other powdery, brightly-colored items are useful for dying grout, according to "Mosaics in an Afternoon." Add powdery colorants until the white powder turns the desired color, or skip this step if you are using a liquid colorant.
Measure water for your grout mixture. Depending on the brand of grout you're using and how thick you want your grout, the water content varies. Consult the grout powder's packaging for the manufacturer's recommendation.
Mix liquid colorants directly into the water. Acrylic paint and food coloring work well as liquid colorants. If you used a dry colorant, skip this step.
Pour the water into the mixing bowl.
Mix the water and powder together with a stir stick, or use an electric drill mixing paddle for larger jobs. Once mixed together, the grout is dyed and ready to use.