The line” But only so a hour” i think it comes a few times in your life, and in the line” Hardest hue to hold” probably means it’s hard to keep what you want for a long time. But overall the whole poem Nothing Gold Can Stay is a poem of not able to hold onto something for a long time.
I think the poem to them means that Ponyboy can't be long for any longer because either socs will find him or either his own gang the Greaser will find the location that he is hiding in and go get him, but then later on after johnny caught on fire that that's when he can't stay on this world for long because