What's the difference?
Skin Color Distribution Around the World
Before the mass global migrations of people during the last 500 years, dark skin color was mostly concentrated in the southern hemisphere near the equator and light color progressively increased further away, as illustrated in the map below. In fact, the majority of dark pigmented people lived within 20° of the equator. Most of the lighter pigmented people lived in the northern hemisphere north of 20° latitude.
(Data for native populations collected by R. Biasutti prior to 1940.)
Such a non-random distribution pattern of human skin color was predicted by Constantin Wilhelm Lambert Gloger, a 19th century German zoologist. In 1833, he observed that heavily pigmented animals are to be found mostly in hot climates where there is intense sunshine. Conversely, those in cold climates closer to the poles commonly have light pigmentation. The relative intensity of solar radiation is largely responsible for this distribution pattern.
So you see, its not the colour of our skin that makes us different. That's just plain geography.