How does Bridie's coloring reflect the sections of this novel?

Bridie's coloring as she grows more and more ill reflect the colors of the novel - Red, Brown, Blue, and Black. When Bridie first has flu symptoms, her cheeks start to flush brighter and brighter red. As her symptoms increase in severity, her skin quickly changes color, going from red to brown to blue. Before Julia can mention her skin turning black, Bridie dies in her arms.