In Chapter 7, Ponyboy says of Sodapop, "I swear, sometimes he reminds me of a colt. A long-legged palomino colt that has to get his nose into everything" (page numbers vary by edition). They are in the hospital, and the press and police are nosing around. Sodapop is constantly joking with the reporters and the police. He steals a policeman's gun as a joke, and he takes reporters' hats and starts interviewing nurses. He acts like a clown to make other people laugh, but, in reality, the situation is grave. Johnny and Dally have been wounded. Ponyboy is expressing the idea that Sodapop is an energetic character who relieves tense situations by making everyone laugh, and he is also a peacemaker. While they are in the hospital, Darry, Ponyboy's older brother, is more serious and conscientious. He soothes Ponyboy and even carries him into his house when they leave the hospital.
Ponyboy goes on to say, "A long-legged palomino colt that has to get his nose into everything." A colt is a young horse who is curious about the relatively new world around him, and he's very playful. This is how Sodapop is when they're at the hospital. He's into everything while they are there and even makes a policeman laugh at his antics. It's a new situation for Sodapop that is exciting, and this excitement infects him. But, Sodapop loses interest in the excitement, just like a young, immature person. He's unable to keep his interest in any one thing for very long.
He would get killed.