What do Johnny's last words to pony boy mean

"Stay gold Ponyboy", this is in relation to the Frost poem. Johnny encourages Ponyboy not to waste his youth looking for things he does't have. Johnny becomes reflective about life using Frost's poem as a metaphor. He tells Pony that life is fleeting and nothing is permanent hence "Nothing Gold can Stay". Johnny encourages Pony to see the goodness in people like Darry instead of wasting their relationship was something it is not. Johnny wants Pony to enjoy the beauty of life while he still ca because, like Johnny's own life, everything comes to an end.