LitCharts assigns a color and icon to each theme in The Color Purple, which you can use to track the themes throughout the work.
God and Spirituality
Race and Racism
Men, Women, and Gender Roles
Violence and Suffering
Self-Discovery
Summary
Analysis
Nettie, in another letter, tells how she and Samuel attempt to convince Corrine that Nettie is the children's biological aunt, and that Celie is their biological mother. But Corrine refuses to believe, even though she has observed Nettie's stomach and has seen no signs of childbirth.
Corrine's refusal to believe attests to the power of jealousy, how it can blind one to the truth despite all evidence to the contrary, how it can tear women in particular apart.