Just curious as to the limits of the range of natural Asian hair colors. Is it almost all brown to black or or other natural shadings possible? Do red or blonde hair ever pop up as part of ethnic Asian genomes without it being related to being albino or some other melanin dysfunction?
There are parts of northern China and Mongolia where people with blond and red hair are…well, not common exactly, but not super rare either. It’s my (limited) understanding that this is believed to be due to some European ancestry; this Discover blog post was the first relevant cite a quick Google produced. Asia is of course right next to Europe and there’s been interaction between the people of the two continents for thousands and thousands of years.
Any place where they might be in the sun a lot (for example, in the tropical or semi-tropical areas), black hair tends to get bleached by the sun, until it becomes a coppery reddish color.
(In Hawaii, hair that color is called ehu.)
People in Asia range from black to pale blond. But I expect you’re asking about east and southeast asia, where colors are typically more constrained, except unnaturally in K-pop, J-pop etc.
A tidbit I’ve found interesting: My partner is Vietnamese, and he’s said that when he first moved to the US, it took him a while to start really noticing hair and eye color, because it wasn’t something he had been accustomed to noting as a distinguishing feature.