Color Fasting makes dark and brightly colored clothes less likely to stain your doll. For this you will need:
Pour 1/4 cup of vinegar and 1tsp of salt into a bowl with approx 4 cups water. Drop in the articles of doll clothing. Swish 'em around a little bit until they are thoroughly saturated with the mix and let them sit for about 30 mins.
Take them out, rinse them with water and a little bit of soap (hand soap will do) in the sink. Let air dry.