How is color important in Chapters 1 to 5?

In the annotations to the Oxford World Classics edition of the novel, Susan Wolstenholme discusses the significance of color in the note about Dorothy's observation of the Munchkins' love for blue. Color is very important in both the novel and the movie; in the latter, the introduction of Technicolor wowed the audience, and in the former a distinct primary color is associated with the three countries – blue for the Munchkins, yellow for the Winkies, and red for the Quadlings. Baum was familiar with color theory, discussing it in his guide to window decoration. Using that theory, yellow is to the west of blue, red is to the bottom/south, the yellow and blue areas intersect in Emerald City, and the china country is trimmed in brown in Denslow's illustrations - which is where the three primary colors meet.