The coloured hair is found in all regions abaayo. Most of the Somali women who don't have pitch black hair dye it because it's not considered as beautiful.
It's genetics though. One side of my family have light brown to red hair whereas the rest have pitch black. Most Africans though have a dark brown hair with red undertones. Very few have black hair like indhayars.
My little brother has it but its most likely from nutrient deficiency, he doesn't eat well. I temporarily had it on the front portion of my hair most likely from the sun , also sea water on my hair drying up from the sun would cause it.