The answer is: It illustrates a sense of misfortune.
In the stanza from "Monet’s ‘Waterlilies’,”the author Robert Hayden makes reference to the Vietnam War and the Civil Rights Movement in America. In the third stanza, he suggests people have a tendency to substitute sadness with joy, and that he is one of the few who sees the tranquility of Money's painting despite the turmoil occurring at that time.