Not sure if i'm allowed to necro like this, but...
How might i describe the properties and composition of this fictional dye in a way that it sounds like it makes sense? (I hate nonsensical Techno Babble in fiction). In my draft it gets analyzed by the law enforcement and they talk about it. It's main thing is that it's blood-red, and seems to never fully come off if you get it on the skin. It might have fallen out of use because of that.
~ * Bleh * ~ (Looking for a russian-speaker to consult about names and words for a thing)To my knowledge, thread necromancy is not a problem here as long as the reviving post is constructive.
Your outer skin (epidermis) constantly regenerates and sheds millions of dead cells every day, which means that long-term stains (like indelible ink or henna) "only" last about a month or so. Unless the dye is inserted below the epidermis like a tattoo, it's going to come off eventually.
Echoing hymn of my fellow passerine | Art blog (under construction)
..uh, no? These are the essential traits of a elementary particle. Without knowing them, one cannot really answer your question. I think that any particle that appears to operate through forces of nature that don't exist in reality would break suspension of disbelief, though.
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." - Richard Feynman