The first person to be seen as racist?

Racism goes back before written history so your question can't really be answered. It most likely was practiced by people in many places at the same time because it is a normal human trait. That doesn't make it right. There are many normal human traits that most people strive to overcome, such as jealousy, retribution, dominance, etc.

I believe that it stems from very early forms of human interaction, when family groups and small tribes feared outsiders and were very cautious of those who were not like them. A trait designed for protection of family and self. Today, we know that you can't judge a book by the cover. We know enough about people and the world around us not to judge others, even those who are different than us, too quickly.