This is a multi-layered question. First of all the question is: are the races exactly the same except for skin color, hair and other insignificant differences? See Race and Species.
While physical differences are quite easy to identify, do they really make a difference? See Differences Cause Conflict.
Perhaps the easiest way to spot what the real problem is would be to take a step back from the fray and look at what is going on right now in the United States of America today on the subject of race. How long can you tread water?.
I hope that will answer your question. You will have an opportunity for further questions later on.