To "stay gold" means to remain unspoiled, pure, and fresh. The line is something that Johnny tells Ponyboy as Johnny is dying. Johnny recalls a famous Robert Frost poem that Ponyboy recited to him when the two were in hiding after their fight with the Socs.

The scene in which Johnny first hears the poem reveals that Johnny has more depth than we have seen previously. The reader already knows that Ponyboy is academic and sensitive, with an intuitive understanding about the people around him. Therefore, it is not surprising that he marvels at the beauty of nature as he watches the sunrise. We have seen this side of Ponyboy before, when he and Cherry watch the moon and he thinks about how universal it is.

However, we get a new side of Johnny in the scene, as he is equally impressed by sunrise. He says,

"Golly … that sure was pretty … The mist was what was pretty … All gold and silver."

He tells Ponyboy,

"I never noticed colors and clouds and stuff until you kept reminding me about them. It seems like they were never there before."

At the sight of the sunrise, Ponyboy recalls the Robert Frost poem, which he recites to Johnny. Johnny is impressed. Later, in the hospital, just before he dies, he tells Ponyboy to "stay gold," which suggests that he understands the significance of the line in the poem, "Nothing gold can stay." His reference to this line refers to the brief and ephemeral stage of young adulthood when a person has their entire life ahead of them.

The phrase "stay gold" is an allusion to the Robert Frost poem "Nothing Gold Can Stay":

Nature’s first green is gold,

Her hardest hue to hold.

Her early leaf’s a flower;

But only so an hour.

Then leaf subsides to leaf.

So Eden sank to grief,

So dawn goes down to day.

Nothing gold can stay.

Essentially, the poem is about the transience of innocence. It illustrates this loss by using the end of springtime as a metaphor. Most people lose their innocence and youthful qualities as they grow up. This is presented in a different way from maturing or becoming less naive, which is a positive experience—instead, the loss of one's goldenness, if it were, is presented as akin to the expulsion from Eden in the book of Genesis, something tragic.

When the dying Johnny presses Ponyboy to "stay gold," he is telling him to retain the positive attributes of youth even after he has become an adult. He wants Ponyboy to remain compassionate, sensitive, and open to the beautiful things in the world (like sunsets), unlike the older teens and adults they encounter who have allowed life to make them callous, violent, and bitter.

While Frost appears to think the loss of innocence is an inevitable tragedy, Johnny seems to believe that certain elements of innocence can remain even in an adult. Once again, not in the sense of being immature or foolish, but in being open to the wonder of life.

Towards the end of chapter 9, Johnny's final words to Ponyboy before he dies are to "Stay gold," which is his way of telling Ponyboy to remain innocent and recognize the positive aspects of life. When Ponyboy and Johnny were hiding out in Windrixville, both boys witnessed a serene sunrise, which reminded Ponyboy of the well-known Robert Frost poem "Nothing Gold Can Stay." In the short poem, Frost explores the transience of youth, beauty, and life using the metaphor of spring's ending. Initially, Ponyboy does not comprehend the true meaning of the poem but recites the poem to Johnny. As the story progresses, Johnny suffers a serious back injury during the church fire and is taken to the hospital's critical care unit.

Following the rumble, Ponyboy and Dally visit Johnny on his death bed, where he references the Robert Frost poem by telling Ponyboy to "Stay gold." After Johnny dies, Ponyboy finds a letter that Johnny had written to him before he passed away. In the letter, Johnny explains the meaning of the poem to Ponyboy by writing,

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. Like the way you dig sunsets, Pony. That's gold. Keep that way, it's a good way to be.

Johnny recognizes the meaning of the poem and wants Ponyboy to retain his childlike innocence and purity. Johnny does not want Ponyboy to develop into a hardened, tough individual like Dally and wants him to remain a compassionate, sensitive person who appreciates the natural environment and is sympathetic towards others.

Johnny alludes to the Robert Frost poem "Nothing Gold Can Stay" by encouraging Ponyboy to "Stay gold" before he passes away in the hospital (Hinton, 126). Initially, Ponyboy does not understand the meaning of Robert Frost's poem, which elaborates on the transitory nature of life and expresses the fact that all good things must eventually come to an end. Towards the end of the novel, Pony finds a letter that Johnny had written before he died, which explains the meaning of the poem and encourages him to "Stay gold."

In the poem, nature's first green is described as being gold, which is "her hardest hue to hold." As time passes, the green leaves wither and lose their golden hue. The golden hue of nature can metaphorically apply to one's childhood innocence and optimism. Johnny understands that Pony has experienced traumatic events, which have resulted in his loss of innocence, optimism, and faith. By encouraging Ponyboy to "Stay gold," Johnny is challenging him to embrace life, remain optimistic, and appreciate the good that still exists in the world. Johnny does not want Ponyboy to lose hope and become callous and jaded like Dally, which is why he encourages him to "Stay gold."

The allusion to Robert Frost’s poem “Nothing Gold Can Stay” is a significant moment in the story. Originally, Ponyboy is confused by the meaning of the poem. After Johnny’s death, though, he begins to realize that “staying gold” is indicative of a complex moral struggle. Things in life start out “gold”—beautiful, innocent, and pure—but change is certain. For instance, the poem refers to sunrise/dawn, early leaves in autumn, and the Garden of Eden. The analogy works for Ponyboy, who grows up significantly throughout the events of the novel. He begins as an innocent boy who goes through difficult and heartbreaking times. Johnny, who dies a hero, can “stay gold.” However, Ponyboy must realize that despite everything, he must stay believing in goodness and beauty (such as the symbolic sunset). Although gold is the “hardest hue to hold,” it is not impossible. Johnny’s final note to Ponyboy causes this important realization, one that he had been struggling with throughout the novel.