Initially, Shug Avery seems litile more than a flashy blues singer who is not only selfish, but also arrogant. However, the key to Shug's character is the element of surprise: Shug always catches us off-guard. In particular, we never expect the self-centered and seemingly superficial Shug to awaken love and self-esteem in Celie, and we certainly never expect Celie to awaken generosity in Shug.
However, just as Celie has never had the opportunity to recognize the potential of herself, Shug has tried to avoid realizing the truth about who she herself is. For example, Shug discarded her name — "Lilly" — and adopted the nickname (not a real name) of "Shug," suggesting a bite of super-sweetness, a quality that is exactly diametrical to the "real" Shug. Shug, in fact, refuses to be "sweet"; she is uncompromisingly honest. Her first words to Celie are "You sure is ugly."
Later, however, Shug befriends Celie, and still later, she becomes her lover. A psychologist would probably classify Shug as bisexual, but the terminology isn't important. The significance of Celie and Shug's sexual relationship is that Celie learns how to be proud of her body and how to use it to enjoy sex.
Celie, in fact, is probably Shug's only authentic friend. Shug, by nature, is manipulative and superficially popular — a free spirit. When Shug is ill, none of the people who seem to enjoy her singing come to see her; they enjoy her music more than they like her. Even her lover, Albert, Celie's husband, doesn't take care of her; he gives her to Celie to care for. Shug, like Celie, never had much affection in her life, especially when she was growing up in Memphis, and although Shug and Albert have three children, Shug is not a "mother." Shug only becomes a "mother" when she begins to love and respond to the warmth that she sees in Celie.
One of the qualities that makes Shug such a "natural" in this novel is the fact that Walker did not, by accident, decide to make Shug a blues singer. Clearly, Shug's being a blues singer is central to her character. The blues are the simplest form of jazz — like "Shug" is the simplest form of "sugar." And the word "jazz" itself comes from a West African word meaning, literally, sperm — and, figuratively, life. In turn, Shug brings a sense of life to her audiences with her singing, and, of course, she brings Celie to life.
Shug is full of life on stage, and she seems to live a sweet life, for the most part, because she enjoys shaking and crooning. However, Shug's "blues" dimension is defined by her selfishness — which leads to lonely isolation. In fact, her love for Albert is reduced to a simple, physical longing for him. He has slighted her twice — by not marrying her initially, and again by not marrying her after Annie Julia died. Shug resents Albert's slighting her; she may be a black woman, but she doesn't want to be defined by someone else's sense of a black woman's worth, or in Albert's particular case, by his sense of a black woman's non-worth.
By nature, especially in her singing, Shug is a "changer"; she starts singing the blues, then turns to a fast snappy ragtime tune. Jazz by its very nature is lovely, unpredictable, and improvisational, and Shug is jazzy because she invents rules and cannot be contained. She is originality. She is a changer, and she effects the most change, ultimately, not on herself, but on Celie.
By being an original, a unique kind of black woman in this novel, one of the things that strikes us most forcefully about Shug is her original concept of God — particularly when compared to the limited concept of the God whom Celie believes in. Shug realizes that although churchgoers may condemn her and her glowing lifestyle, God himself, or itself, does not condemn her — because he, or it, is everything. Shug postulates that it is a sin to be miserable and unappreciative of the world and its beauty.
Finally, Shug is the color purple personified. She is both red and blue simultaneously. Red represents jazz and life, and the blues' origins are in misery and disappointment. Together, red and blue create purple.