You Gotta Have Blue Hair: Not all the uses of genetic engineering – or other technologies, including that shampoo that turns regular hair into a fully-functional LCD display surface for a week or two – are for even vaguely utilitarian purposes. Enough said.
(As a side note, the silvertouched – see Our Dwarves Are All The Same – do this naturally with some metallic colors, due to their symbiotic silverlife accumulating metal within their bodies, which turns into metallic strands in among their hair, among other things.)
This is a companion discussion topic for the original entry at https://eldraeverse.com/2016/03/11/trope-a-day-you-gotta-have-blue-hair