it's called "genetic diversity"
you didn't fall for the "all shitskins have the same black hair and muddy eyes" meme, did you?
Where do ssa blacks get their grey eyes from? Or is it just some kind of depigmentation process related to old age?
There are multiple different polymorphism on HERC2 (and some on OCA2) that are known to cause blue eyes.
One of them (which is particularly benign) is extremely prevalent in Europe, but sporadic cases of it elsewhere are generally unrelated.
Btw, huskies have a completely unrelated mutation on ALX4 which also gives them blue eyes.