Why does Scottie stop working as a detective?
In the first scene of the film, we see Scottie working as a detective. He is pursuing a man alongside a cop and ends up falling from a rooftop and hanging off a ledge. In the process of hanging, Scottie experiences extreme vertigo, which completely debilitates him and even leads to the death of his partner, the cop. As a result of the incident, Scottie decides to retire from his job as a detective to take some time off.
Why does Midge get so upset after Scottie responds poorly to the painting she did?
Midge is jealous of Scottie's infatuation with the mysterious Madeleine, so devises a plan to make fun of the case. She paints a large reproduction of the Carlotta Valdes portrait with which Madeleine is so obsessed, but then puts her own bespectacled face in the painting as a kind of ironic joke. Scottie, who is in deep with Madeleine and takes the case very seriously, does not see the humor in Midge's gesture and leaves in a huff. Midge gets upset because she realizes that her plan, which was meant to bring her closer to Scottie, has done the opposite. She blames herself for driving away the man she loves.
What is the purpose of Midge's character?
While Midge does not serve much of a purpose to the central plot, apart from acting as a confidant for Scottie and introducing him to the historian/bookseller Pop Liebl, her relationship with Scottie is a kind of foil for his relationship with Madeleine. Where Madeleine is ethereal, mysterious, elegant, and disturbed, Midge is pragmatic, self-aware, humorous and straightforward. She often behaves in a maternal way towards Scottie, even calling herself "mother" when she goes to visit him at the sanatorium. It is precisely these attributes that turn Scottie off of Midge, and the qualities that make Madeleine all the more unusual and aloof are what attract him to her. While it is not explicit, Hitchcock frames the two women as opposites: one is maternal and knowable, while the other is elusive and unknowable.
What piece of information do we learn that Scottie does not, about two-thirds of the way through the film?
After Scottie meets Judy and arranges to meet her for dinner, the viewer is left alone with Judy. In this moment, she drafts a letter to Scottie informing him that she is in fact "Madeleine," and that she was hired by Gavin Elster to pose as his wife. The woman whose body fell from the bell tower was Gavin's actual wife, whom he killed by strangulation. In fact, Judy is the woman with whom Scottie fell in love, only now she is being herself, rather than playing a character.
How does Hitchcock use color and light to tell his story?
One of the most striking color motifs in the film is Hitchcock's use of the color green. When Scottie first sees Madeleine, she is wearing a flash of green. Then later, when he meets Judy, she is wearing a green dress, and her hotel room is illuminated by a bright neon green light that shines outside the window. In the moment when Judy emerges from the bathroom, her hair done up in the exact way that Madeleine used to wear it, she is completely lit by green light, which seems to cast a strange halo around her whole body. In this moment, she looks like a ghost come to life (and indeed, in a sense she is).