Green at dusk and nile at noon Have much to commend them for their hues; If choice of color is mine to choose Green at dusk is the one I make.
Light of morning wakes rye to green The sun will bleach as day grows large; Let clouds erupt a powered charge, The shock turns fields to emerald.
But twilight keeps a dyestuff for The heart's wry mood, as hills expose A nib of gold that burns and goes Out, embered in sunlit amber.
The speaker is playing a kind of favorites game with colors. Green at dusk and the pale green of "nile" at noon both have their charms, but the speaker decides firmly on dusk. The second stanza explains what the other greens lack: morning light turns rye green, only for the sun to bleach it out as the day wears on, while a storm can electrify the fields into a sudden, almost shocking emerald. Those greens are either fleeting or dramatic.
Twilight, the third stanza suggests, offers something quieter and more personal. It suits "the heart's wry mood," a feeling that is knowing and slightly bittersweet rather than plain happy or sad. The closing image, a small "nib of gold" on the hills that burns and then goes out like an ember, captures that mood well. The poem feels calm, reflective, and a little wistful, finding beauty in the moment just before light disappears.