Talk to him and explain how we are all different but the same. Explain how people should not be treated differently because of the color of their skin. This is a good time for you to read stories and to do a little research on the internet to help your child learn about different types of history. Give him examples of people of different races that have mad a difference in society; for example, Dr. Martin Luther King Jr. who fought for equality for ALL people. President Barack Obama who is the first African American President. Here is a wonderful website with different culture accomplishments: https://www.biographyonline.net/people/people-who-made-a-difference.html. There is an abundance of information available to digest. Use google as your search engine because it makes it easier to search.