According to The Wrap, "Yellow stars Cassavetes’ ex-wife, Heather Wahlquist, as Mary, a beautiful woman addicted to pain pills. She searches for a stable place back home in Oklahoma after being expelled from her teaching job in L.A. for having broom closet sex on parent night. (Wahlquist, who co-wrote the film is from Oklahoma. Melanie Griffith plays her mother, and Sienna Miller is her hysterical sister.)"
The married director (and father of two) defends the main character's incestuous relationship by says people should do what they want.