if he spit purple, maybe it because he heating his crayons again.
Purple is color of elemental Iodine vapor, or elemental Iodine dissolved in a solvent such as cabon tet. But in the body it is not purple as the elemental form is highly reactive, reverts to iodide, which is colorless.
So if someone spits purple it cannot be iodine, and if they believe it is iodine, then they will have a hard time to find their answers