An example of a lesson Ponyboy learned is that people can’t be labeled. He realizes that just as he does not like being judged for being a greaser, he should not judge Socs.
When Pony meets Cherry, his attitude toward Scos changes. His preconceptions are tested. He has stereotypical views of Socs as spoiled rich kids, and knows that Socs and others stereotype greasers as well. He realizes that while the two social classes are different, they have more in common than he thought. Cherry is a decent girl, and is willing to listen to him.
Maybe the two different worlds we lived in weren't so different. We saw the same sunset. (ch 3, p. 41)
Pony realizes that although people belong to a group and share similar characteristics, all people cannot be considered the same. Not all Socs act alike, and not all greasers act alike. Pony even gets to know Randy later, and sees more nuances of similarity and difference. Not all Socs want to fight.
As Pony gets older, he starts looking at people as individuals rather than members of their group. He wants people to look beyond his long and greasy hair, and he realizes he has to do the same.