Why do communists try to exploit racism?

This answer assumes that we are talking about the Cold War.

Communists historically have not had a problem with race; they fight ideologically. A non-communist is the enemy of a communist no matter what race he is and a communist is a brother of a communist no matter what race he is. However, most capitalist societies have inequalities that do run along racial lines, leaving a number of races feeling disaffected in their home countries. A perfect example of this would be the African-American population in the United States. As is typical in spycraft, you target individuals who are more susceptible to conversion to your ideology. For example, an African-American who was disaffected because of the rampant racism in the US in the 1950s and 1960s would be more prone to accepting a Soviet Communist message that teaches true equality for all communists than a White man who is generally has a more favorable view of the United States government.