I've got dark brown hair, but the little hair on my arms for instance is very light - clearer than blond. I think the wild variation is fairly common for Slavic types. I'm probably lucky in that my leg hair has always been very sparse and light blonde in color. I know why their hair doesn't match. I got accused of being a "bottle blond" a LOT when I was in my teens and 20's. Which I think is the answer to your question--different races have different dominant genes, and there are separate genes for, say, your chest hair and the hair on your head. I've known women who had dirty blond hair and had black pubic hair.
How Can I Get Blonde Pubic Hair That Looks Natural?
My chest hair is dark brown.
Betty Beauty Blonde Pubic Hair Dye
What color is your underarm hair? My eyebrows are a light-to-medium brown. Given that hair should be the same all over This is not even vaguely correct.