The answer is: foul, dismal, stare
In literature, the tone refers to the attitude of the author towards a certain topic. In the excerpt from "The Great Gatsby," the writer Francis Scott Fitzgerald directs attention to the Valley of Ashes, which symbolizes poverty and despair on the one hand, as well as the immoral values and degeneration of culture. As a consequence, the author uses words that express a negative and gloomy overview of Gatsby's American society.