What do you think the speaker means when he says, “Nature’s first green is gold”? HELP

In me thou seest the twilight of such day, as after sunset fadeth in the west, which by and by black night doth take away, death's second self that seals up all in rest. —"sonnet 73," william shakespeare read the second quatrain of “sonnet 73,” and then answer the questions. what is the best paraphrase of these lines? what is the central idea of these lines?