Gentle and a little heartbroken, the poem follows a speaker who spots a white butterfly resting on red roses they planted for it. The speaker talks directly to the butterfly, asking if red roses are still its favourite and admiring its colour, which they call "you-white," a shade that belongs only to this one being. That invented word makes the butterfly feel personal and irreplaceable.
The butterfly may be just an insect, but the way the speaker says "I've really missed you" suggests it stands for someone they have lost. That is an inference from the text, not something the poem states. Either way, the speaker knows the visit can't last. They wanted it to stay, yet they let it go, saying goodbye as it flies off.
The ending is the most moving part. "For now, never, and forever" holds hope, finality and permanence together, as though the speaker can't decide how long this goodbye will be. The mood is tender, quiet and bittersweet.