I have met white Christians who claimed that all people were originally white and that black people are children of the devil and I have met black Christians who claimed the opposite. Both use the Bible to prove their statements. I ask myself the question, what skin color really was first; what do today's science and the Bible say about it?
Short answer: I don't know. I believe Adam and Eve were the first people. Some people believe that the garden of Eden was in the inner earth. In which case does that mean they were light skinned because lack of sunlight? But there would have to be light in the garden of Eden for plants to grow so I doubt that. If the garden is in the inner earth it doesn't prove anything either way.
Others claim that Adam was made from red earth which made his skin red. However, I'm not sure that it works like that. It may be true; but it's not necessarily the case that the color of dirt would dictate the color of one's skin. Really the color of one's skin is due to the amount of melanin which is genetic. So again it doesn't prove anything either way.
I don't believe skin color denotes the children of Satan. Rather the actions people do.
The fact is every skin type has advantages and disadvantages. As you point out with your graphic darker skin is better in areas with a lot of sun exposure because it resists burning. On the other hand lighter skin is advantageous in areas with little sunlight throughout the year. The reason is that it absorbs vitamin D faster from less sunlight.
Mid range skin tones are the overall most adaptable and light skin seems to be an adaptation for people living in more overcast northern climates whereas very dark skin seems to have been an adaptation for people living in very hot areas of the globe.