All of the artwork is in black and white. The visual iconography is interpretable as western, which is thematically appropriate for this work; Marji and her society are struggling to maintain their westernized/modernized ideals and identities against The Islamic Revolution.
The strict use of a black-and-white color scheme is common in graphic novels but it works thematically also. Early in the novel, Marji reveals that she believes she is the "last prophet."
Marji does not see in "black and white" the way the Islamic Fundamentalists do.