We have found that in some instances if Veil is applied to especially UV-damaged plastic headlight housings then there is a potential of a slight violet-ish residue that can be left behind which can be removed with wet-sanding and polish/plastic restorer.
However, we recommend that such headlight/plastic housings be "repaired" before applying Veil, because your light output is probably already compromised.
Of course, Veil is not meant to go on a vehicle's painted surface. It is meant to be applied either to the headlights, foglights, and/or license plate covers, that's it.
Hope this sufficiently answers your question.