Crayon stains appear as built up, shiny and stiff stains in a variety of colors. Normally, drying--not washing--will cause these kinds of stains.
Your first discovery of the stains will occur when you open the dryer door to find otherwise clean clothes covered with a myriad of colored stains. The stains appear after drying because the heat from drying melts the crayon material.
The easiest way to solve this problem is to take the garments to your drycleaner, who usually can remove them by running the garments through a dry cleaning machine. If any of the stains remain after cleaning, they can generally be removed by your drycleaner through traditional stain remoal procedures.