Other than French ones, I can't recall ever seeing images of African troops in greatcoats, I'm afraid. Not in Africa, at any rate. Before WW2 the French were the only power to use their African troops extensively outside of Africa. You'll see plenty of tirailleurs in greatcoats in WW1, but they don't really look like these guys, and there are already perfectly good figures of them available from firms such as Gripping Beast.
I'm struggling to see a use for them in a 19th Century colonial context, I'm sorry to say. Maybe Germans (i.e. white troops) in South West Africa or East Africa if you gave them sunhats? Maybe?