On a more serious note relating to the OP, I think there has been a misconception and/or misinterpretation of things. Instead of people actually getting whiter in color, I believe that people who find joy and happiness through living the Gospel show it in their countenance. You can usually tell a person is happy and confortable with who they are before God by how they look outwardly, and you could say that some people are positively glowing. That does not mean that a dark-skinned person actually turns white, but that they have that 'glow' of the Gospel about them. That glow comes from within.