Atticus, Jem and Scout are most certainly white, but they represent the individuals closest to the boundary between the black and white communities in Maycomb (except perhaps Dolphus Raymond). Atticus is content to defend any man against injustice and accepts his cases on need and merit, not colour. He extols his egalitarian values to his children, Jem and Scout, and strives to teach them to consider each individual in terms of character rather than colour. It would be interesting to consider how different the story would be if these main characters were indeed black. Of course Atticus would not be a recognised legal representative, and the children's perceptions on the ways of society at the time may be tinged with more fear and trepidation than the real Scout and Jem show.
Rizelle, I do believe you need to read at least the first chapter of To Kill A Mockingbird to find the answer to this one. One of the main characters of the novel, Tom Robinson, is black, and his rape trial becomes the main focus of the middle portion of the book. Atticus Finch serves as Tom's defense attorney, and he earns a place of honor and respect in the hearts of Maycomb's black citizenry. Calpurnia, Atticus's maid, is also black, and she serves as a second mother to Jem and Scout.
They are not Black people, however they see the struggles of black people. Atticus teaches his children who are subjected to the horrors of Jim Crow that that way of life is unacceptable. How the children are confused by the actions those that are prejudiced is a lesson that Atticus must teach due to the relationship the children has with their caregiver, and the injustice done to an innocent man (Tom Robinson). No they are not black, but the lessons they learn helps them to respect that there is no difference between human beings.
No, they are white people that recognize the injustice of their community towards black people. Atticus takes a stand against the injustice that occurs against Tom Robinson just because he is black. Tom Robinson represents the whole black community and the injustice they face throughout the novel.