The stain may be permanent, but the first priority is to remove all of the crayon residue. Crayon is wax based, so anything that dissolves or softens wax will help remove it, but be aware that some of these things are flammable [like paint thinner] and somewhat toxic.
First thing I would try is Zep Purple degreaser. It is a concentrated version of the same active ingredient in Fantastic but it isn't flammable. Use rubber gloves and a non scratch scrub sponge.
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Try diluting it about 2 parts water to one of the concentrate at first, if that doesn't work try adding a little more concentrate. Full strength may take the shiny finish off of you dryer drum.
You probably want to use a face mask while using it; get one for paint odors or organic vapors.
3M Tekk Paint Odor Valved Respirator 2 Pack
You should take off the vent hose and try to get as much of the crayon out of the vent passageways.
If the degreaser doesn't work try orange oil cleaner
If the orange oil cleaner doesn't work, odorless paint thinner may, but it will have to dry first and you will have to make sure you have all fumes out of the dryer before using it. Put a fan on the open dryer for 8 or more hours.
After you get it as clean as you can, run a few loads of things that won't matter like work clothes or jeans.