The chart above shows the family generation of a small community in Kentucky. They had a weird skin pigment that changed their skin blue. It was started to spread because many people had babies with their own cousins. Its kinda gross but the gene was passed down from generation to generation. It was a dominate gene early in the generation because it was a small community and most family members had kids together. As the town started getting bigger due to mining the blue skin started to fade away. Many doctors didn't know why their skin was blue but it was very interesting. This was a very interesting article, their was so much information on this generation of blue people.
http://www.indiana.edu/~oso/lessons/Blues/TheBlues.htm#pedigree
http://abcnews.go.com/Health/blue-skinned-people-kentucky-reveal-todays-genetic-lesson/story?id=15759819#.T0voNlFTNSq