Afars are much darker than Somalis.
I think that has more to do with them living mostly in the Danakil desert:
Like why Somalis from the qurbo are much lighter on average than their homeland counterparts. More sun. I bet if you took Afars to a place like Sweden for a decade or so, especially since they have more Habesha-like ancestry than us by the looks of it, they would lighten up and be similar to qurbo Somalis.