Sunsets and Sunrises
Sunsets and sunrises in The Outsiders represent the beauty and goodness in the world, particularly after Johnny compares the gold in the poem "Nothing Gold Can Stay" to the gold of the sunrises and sunsets Ponyboy enjoys. The sunset also stands for the common humanity of all people, regardless of the gang to which they belong—in their first conversation at the drive-in, Cherry and Ponyboy find common ground in their enjoyment of the same sunset from opposite sides of town.
The greasers' long, slick hair is a symbol of their gang, both to themselves and to others. When Ponyboy and Johnny cut and dye their hair while in hiding they're taking a symbolic step outside the gang. As a result, Ponyboy feels less secure, but also gains a bit of room in which to develop his individuality.
The Blue Mustang
The blue Mustang represents the Socs wealth as well as the danger they pose to greasers. When Ponyboy or another greaser spots the Mustang, he knows trouble is coming. As the novel progresses, however, and Ponyboy comes to understand and feel compassion for the Socs, the Mustang loses some of its power to intimidate. Ponyboy actually sits inside of it when Randy and he talk about the church fire and the rumble.