Hanna Yarker, from Sale, Greater Manchester, started noticing the difference between the sisters some time after they were born.
It dawned on her that while Anaya had taken after Yarker's fair skin and light eyes, Myla's complexion resembled her darker-skinned father Kyle Armstrong, who is mixed-race.
"The babies were identical for a while, their skin had a sort of purplish tone," 20-year-old Yarker told Sputnik. "After about three weeks they started becoming more and more different, starting from the color of their eyes."
"Both Kyle and I were in a sort of shock when the girls began to change," she said.
Unlike identical twins, who are born when a woman's fertilized egg splits into two equal halves with an identical genetic makeup, unique looking twins develop in different amniotic sacs and take different genes from each parent.
Skin color is coded by one to seven genes, which blend together in mixed-race people. In this case, Myla received her dad's "darker" genes, while Anaya took the genes begetting a lighter complexion.
Yarker said that the 10-month-old sisters, who were born just a couples of minutes apart, still have generally similar facial features, and they often sport identical outfits, in the best twin dress-code tradition.
Nevertheless, this hasn't stopped strangers on the street from questioning Yarker and Armstrong about their uniquely different babies.
"People are always surprised, and keep asking me all sorts of questions," Yarker said.
"The main ones are 'are they really sisters?', 'are they related?' Somebody even asks whether they are my kids at all."
