Unlike crayons, spraying on crayons makes it last longer outdoors. Now all you have to do is buy some crayons, watch some online tutorials and you can get started; you already have WD-40. We wish you good luck!
You will probably give them back their pristine white color (if they were white). An efficient way to accomplish this is again with WD-40. Spray, wipe, done. In no time, your chairs will be as good as new again and you won’t have to make any more excuses not to invite your guests outside.