The red/white dichotomy arises often and explicitly through the course of the film, both in the form of the red flashes typical of Marnie’s panic attacks and the red stimuli that cause them.  We are later to learn that the red/white relationship arises directly from Marnie’s “accident,” in which she spilled the sailor’s blood across his white shirt. Though this device appears simplistic, it serves, in much the same way as Scottie's dream sequence in Vertigo, to draw the audience into direct relation with the character's psychological state.1 As Marnie comes to a fuller understanding of her "accident," the diegetic red triggers more directly take the form of the accident. The result in the audience is an especial empathy with Marnie's state - and an especial personal interest in solving her mystery.

Marnie's first flashback, at her Mama's house, is triggered by red flowers.

Her third flashback is, once again, triggered by red ink staining her white shirt. Hitchcock's gradual revelation of the surface mystery of the movie is by now evident: visually, this example is more similar to the truth of the accident.

Marnie's fifth flashback also revolves around diagetic red: for the first time, we see a man with red spots on his shirt.

The evolution of the red/white relationship, by way of its relevance to the plot, is intimately entwined with the evolution of the flashback music, which, broadly, I term the Sailor Motif. Note the progressively more clear statements of the theme as the flashbacks progress: these parallel the exposition of the mystery in the same way as the color dichotomy.