What does it mean to "stay gold"?

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.