The structure of The Color Purple is composed of a series of letters written by Celie to God and her sister, Nettie. Some letters are also penned by Nettie to Celie. This style, known as an epistolary novel, was first popularized in eighteenth-century England by writers like Samuel Richardson. One major advantage of this format is the strong bond it creates between the reader and the letter writer. Through this narrative form, Walker explores her protagonist's inner world, crafting a sense of closeness that likely contributes to the novel's success. It enables readers to feel as if they are peeking over the character's shoulder, gaining an understanding of her thoughts and emotions.

Nettie managed to avoid much of the harshness that Celie faced by leaving home at an early age. The tone of Nettie's letters to Celie is noticeably different from Celie's letters to God. Nettie's letters are less personal and do not express the same depth of suffering. By including Nettie's letters, Walker shifts the story from Celie's despair to a budding sense of hope. It is with the help of Shug Avery that Celie finds hope, specifically in the letters from Nettie that Albert had hidden from her.

The novel is divided into four main time periods. Initially, Celie suffers under the weight of poverty and cruelty imposed by her stepfather. In the second phase, she continues to experience abuse from her husband, Albert. The third period marks her journey to self-awareness through her relationship with Shug and restored connection with Nettie. In the final phase, Celie attains self-realization, gaining control over her life and finding happiness and fulfillment. Additionally, Nettie's experiences in Africa, although not directly linked to Celie's life, contrast with Celie's experiences and expand her viewpoint, helping to universalize her journey.