This article will show you how to remove stains from colored clothing. The difficulty level of the task will depend heavily on the stain you are trying to remove and how long the stain has been there.
Before you do anything, you should soak the stained area in some sort of laundry pre-treatment, or stain remover. A great option is Spray n Wash, or OxyClean.
Allow the stain to sit and the chemicals to work through the area before you wash the clothes.
Wash the garment, and repeat if necessary. If you have powdered OxyClean on hand, add some of this to the load to help keep your colors bright.