Because of the way Decker’s brain is wired, he experiences colors as something more than visual stimuli. Both in his memories of past events and in his current investigations, Decker associates particular colors with specific emotions.

The most prominent color for Decker is blue because he associates this with the murder of his family. His choice of adjective to describe the color evokes emotion, as he calls it “terrifying.”

Other colors maintain a consistent association for Decker and move to prominence depending on his mental state. Just as he associates blue with death, he associates white with despair.

He also describes various characters by color whom he doesn’t like. The con man is purple—worthless, and Leopold is yellow—cunning. He sees Wyatt as gray—a color with no definite associations.

For a normal person, numbers serve an intellectual function to measure and calculate. However, Decker’s brain processes numbers in a way that contains emotional resonance.

Numbers recur in the novel in the same way that colors do, as Decker assigns them to feelings and people. He mentions “six” as being a dirty number. “Four” is uninteresting. “Zero” is an unwelcome digit.

The number that looms largest in Decker’s mind is “three.” It lunges at him out of the darkness as a frightening hallucination portending danger.