You need to be a bit careful relying on artificial markings to identify hogs. I have seen hogs which have seemingly had marks on top of other marks (possibly by another person) and also individual hogs which have been re-marked in a different pattern to the original. So the only safe way to be sure it’s the same hog is to learn to recognise them by their natural markings.
Of course artificial markings can make that a bit more difficult. For instance a hog may suddenly turn up with half a dark face which it has, presumably, got from biffing another hog. I hope, at least, that no-one is purposely putting artificial marks on any hedgehogs’ face.
But it also has the effect of seeing the hog as the marks on it, rather than as the hog itself – it draws attention away from their natural markings which are part of the intrinsic nature of the hedgehog.
As said many times previously, I see no need to artificially mark hedgehogs. They have their natural markings, but if anyone does mark hogs, it should only ever be on the tips of a very few spines, kept well away from face and the skirt and ensuring that it doesn’t reach the skin. Substance on the face could cause eye problems. Substance on the skirt area is more likely to be ingested, which isn’t going to do the hog any good. Hogs often have slightly different colouring on their skirts (a bit like a hog barcode!) but I have often seen artificial marks on the skirt, and skirt band. Pointless, when there is already natural marking there. We only need to look.