Gold represents innocence and childhood. The phrase "Nothing gold can stay" means that nothing can stay young forever. People will age no matter what; people will lose their innocence no matter what. In the letter Johnny left Ponyboy inside the copy of Gone With The Wind, he says, "I've been thinking about it, and that poem, that guy that wrote it, he meant you're gold when you're a kid, like green. When you're a kid everything's new, dawn. It's just when you get used to everything that it's day."
This poem relates to The Outsiders because Ponyboy Curtis was just fourteen-years-old and was already facing so much in his life: murder case, parentless, brotherhood. Ponyboy has seen and heard too much to be innocent, yet he is not dirty. All this is making Ponyboy "lose" his "goldness", yet there is so much that Ponyboy is doing that keeps him gold, such as watching sunsets. Ponyboy has a childlike view of the world, and when Johnny tells him to "stay gold", he wants Ponyboy to stay this way and to never let go of these young, innocent things.
