Adam and Eve were never white, because they never existed.
Evolution exists, and black people exist because we were here far before you (Caucasian) people were. Ever noticed how Native Americans aren't caucasian? And how the only reason Americans are depicted as such is because the Europeans slaughtered the Native Americans? Yeah, making any flipping sense now? -.-'
The Bible never stated any of the skin colors of the recorded people there. All these assumptions are due to the various paintings of the people from the Bible that we all know and are familiar with. Most of the paintings have been made during the Renaissance period, and more or less the painters used their own skin colors as basis.