If you bought mohair listed as “natural black” would you expect it to be dyed? I bought some long time ago; it is gorgeous, but came tied in little bundles tied with something black. It was not until yesterday when I started to root with it that I realised that the mohair is dyed; it’s very obvious the black string is dyed.
By the way, I wish more sellers would sell their mohair tied in bundles. I then just cut off 1 strand as I need it and the rest is safe from getting messed up. You lose the little bit on the end but are so much less likely to waste the rest.