Nature first green is gold orients us to the setting as well as the overall theme This is a classic metaphor because Frost isn't literally saying though that green is gold however he is attempting to hook the reader into believing that there is a certain wealth or value to nature's first green which I interpret Frost is speaking about spring.
Frost captures us further with some alliteration in line two phrase to Mother Nature as he claims that this color gold, which could be a simple nod to the sunrise as it Peaks Over the Horizon as much as it is truly about the color gold, is her hardest Hue to him. I believe frost a showing us this fight a temporary flash, or the cop and circumstances of wealth, gold, or richness, it is indeed temporary, thrus, it's difficult to