Hi Richard
Hedgehogs have individual natural markings as with any animal, if you look carefully enough. Things to look out for are facial markings, colour variations on different parts of the hedgehog – face, spines, skirt, band between skirt and spines, even legs sometimes have different ‘blotches’ on different hogs.
I wrote some more detailed suggestions in the following:
https://www.hedgehogstreet.org/forums/topic/tolerant-hedgies/
For the sake of the hedgehogs, please don’t be tempted to artificially mark them. It is wrong, for so many reasons. The following is some information from BHPS FAQs:
Can I ‘mark’ my hedgehogs?
We’re pretty sure a hedgehog would rather not be marked, but if you are going to do it, please do ensure that you use a non-toxic water-based marker and mark just a few spines of the hedgehog. Keep the mark away from the hedgehog’s face and mark it in the garden on the ground rather than picking it up/bringing it indoors. Please don’t use red as people may mistake it for blood and ‘rescue’ it. Do not make hedgehog conspicuous to predators. We have seen some very sad images of poor hedgehogs practically covered in paint! If you are watching the hedgehogs on a wildlife camera you will often be able to tell them apart over time without the need for marking.
