Sofia's speech at the dinner table was an ad-lib prompted by Steven Spielberg, in the middle of filming the scene. He asked Winfrey to express to Celie how she felt that day when she saw Celie in the store, as Sofia was shopping for Miss Millie.
Before production, Steven Spielberg felt very insecure about being director of the film. In fact, his initial response to Quincy Jones' request was no. Spielberg felt that his knowledge of the deep South was inadequate, and that the film should've been directed by someone of color, who could've at least related to the struggles faced by many blacks living in the old south. Jones then argued, "No, I want you to do it, and besides, did you have to be an alien to direct E.T. the Extra-Terrestrial (1982)?" Spielberg appreciated his friend's logic, and decided to take the role as director of the film.
Steven Spielberg's first baby was born during the filming of this movie and he was serendipitously called away from the set while preparing the early scene in which Celie gives birth, leaving the scene to his assistant director. Spielberg later used sounds of his newborn crying in the same scene of Celie giving birth, which he had to miss directing.
In the Turner Classic Special "Spielberg on Spielberg," Steven Spielberg cites The Color Purple (1985) as his first "serious" film, and that he would have not been able to do Empire of the Sun (1987) and Schindler's List (1993) without the stepping stone that was this film.