Answer:
Discontent.
Step-by-step explanation:
The tone is described as the author's approach or attitude towards a specific subject matter which is reflected through the diction or language adopted by him/her. It primarily functions to provide the readers with a perspective to view the text and the feelings or emotions to be elicited after reading it.
In the given excerpt from 'The Outsiders', the author displays a tone of 'discontent' to display the resentful feeling of Ponyboy towards the greaser girls which is clearly reflected through his regretful statement 'I thought.' Thus, it provides readers with a framework to perceive Ponyboy's felicity and show feelings of empathy for his situation.