LitCharts assigns a color and icon to each theme in Paper Towns, which you can use to track the themes throughout the work.
Perception vs. Reality
Authenticity and Artificiality
Human Connection
Leaving Home and Growing Up
Friendship
Summary
Analysis
Quentin remarks on all the new things he has learned about himself while driving: that he is willing to pee into a mostly-empty bottle of Bluefin energy drink, which he and Radar have been drinking to stay awake, and that he appreciates the turquoise color urine makes when combined with trace amounts of Bluefin.
As their trip crawls forward, Quentin is losing his last, most basic pretentions, peeing into bottles as he mocked Ben (even if in a friendly way) for doing just hours earlier. In a trivial sense, he has even mis-imagined himself — he never expected to be doing all this.