If you want a real answer, they turned white. All our races are offshoots from a central cradle of civilization (wherever that cradle might be, some say Africa, others the middle east, yet others somewhere near Greece). From that branch-out, ones moved south and needed darker skin to resist the sun, those with paler skin got too burned and died/mated inefficiently, while those who moved north needed paler skin, and those with dark skin died/mated inefficiently due to vitamin D deficiencies. At the starting point, they would have all had more or less the same skin tones, but over time, the micro-evolution would become macro-evolution.

This would have all been long before photography, or even modern painting techniques, however.