That current skin colour itself is only skin deep is an old but apparently true saying. Skin colour itself of a race is probably not fixed forever but is affected over centuries by the strength of the rays from the sun, that too seems to be fact.
Historians tell us that humans originated in Africa and we are told now (surprise, surprise) that early humans in Britain had dark brown skin, not the light coloured skin of today! See: Brit 10,000 years ago
Also, as we know, there is a slight variation in facial characteristics of differing human races on earth though for almost the whole of our build we are all alike with two ears etc. etc.