In the book Heaven’s Ant Farm, the only survivors of Heaven’s Holy Nuclear War were forced to live in underground caves for 2,000 years. When their descendants came out from their underground sanctuary, they realized something had changed. They were all the same color.
But the original 5500 survivors who went in underground to escape the war’s radiation were of different races and colors. The contrast between black, white, red and yellow skin tones prevalent before the Holy Nuclear War slowly faded away.