Ray Bradbury depicts the citizens as gray because they are spiritually dead, empty of imagination and the warmth of humanity. They watch the parlor walls and live their lives dully indoors and experience life only vicariously by watching mere shadows on the walls.
In Part III, Montag is made to set fire to his house after his wife Mildred has reported him for having books. Beatty, who gives the order, does not understand that Montag takes some pleasure in the burning as he is disgusted with the sprawling parlor wall screen that has ruled the life of his wife. She is like the other people whom he later sees watching the broadcast of the manhunt for him, "silhouettes of people inside watching their parlor walls...." As he flees, in a nightmarish image, Guy imagines thousands of faces searching for him:
pale, night-frightened faces, like gray animals peering from electric caves, faces with gray colorless eyes, gray tongues and gray thoughts looking out through the numb flesh of the face.
Gray is a neutral color; often it is the color of something that once was some other color, but is now faded. Gray is often the color of the dead or the sickly who have been shut in for long periods. In Montag's perception, the people peering into the yards and alley are the like the people of The Allegory of the Cave by Plato, people who have known no reality, only shadows on their walls. Like Mildred, who does not understand her husband or love him, they know only the shadows on the wall. Unlike Clarisse, they have never ventured outdoors, living only in the shadows made by artificial light and never having a genuine conversation. Their souls are deadened; their faces lifeless.
Truly, their appearance is eerie, for they have lost their hearts, their spirits, their humanity. They live only vicariously through imaginary characters on their walls. But Montag's soul is "burning bright" and he runs for his life, his spirit, his soul, heading toward the community to which Faber has directed him, a community in which people have not surrendered their souls and imaginations.