Please pick up a book called "Africans and Native Americans:The Language of Race and the Evolution of Red-Black Peoples" by Jack D. Forbes.
It discusses the arbitrary and inaccurate nature of racial classification in the US. Forbes does a great job of showing how many Indian tribes in VA had their land stolen by an early form of the "1 drop" rule. In many cases he found that full-blooded Indians were being called "negro" and "mulatto"! It really goes a long way to explain the way colonizers attempted to legislate Black Indians out of existence. Relatives I thought were black African turned out to be mixed with Indian or full-blood. It cleared many things up for me in research my own family history. I hope it helps someone else do the same.