How to prevent stains?
Washing the doll clothing first
You can fix the color of clothing a bit more to the fabric by washing them with water and vinegar. Leave the clothing for some time in a good mix of 1/2 water and 1/2 vinegar. So the excess color will be washed out. The piece will be more likely not to leave stains as much as before. Make sure to wash off the smell afterwards. This is not a guarantee anyway but it may decrease the result of staining.
You should also have the colors of the different pieces in mind. So they will not color each other or anything similar! Try not to leave your dolls in dark or black clothing for too long. For myself I always dress my Dollfie Dreams in lighter colors. After use of a “dangerous” colored outfit, like after a photo session.