What is the theme in Bluish by Virginia Hamilton?

All three girls in the novel - Dreenie, Bluish, and Tuli - are struggling with the ubiquitous challenge of fitting in. For Dreenie, she is the new kid to class and is having difficulty making new friends beyond Tuli. Dreenie is also battling feelings of inferiority with respect to her "genius" younger sister Willie. She is worried about whether or not she is a "dumbbell" and wondering what her place will be in life.