Skins for Spells and Animation Effects

I've seen many skins for unit models, but I haven't seen one for spells and animation effects. So I'm asking you, can spell skins be changed as well as unit skins?

I´m not 100% on this but, I think most of the spells skin can be changed. Seeing as they´ve got to be connected to a blp, the trick would maybe be finding which blp they use. I myself have once changed the skin of the green thing that tha acolyte gets over his hand when mining, so at least things like that are easy to change.