A Route of Evanescence (1)
Part of the reason why the hummingbird is so amazing is because the speaker can't quite put into words what she just saw. A bird's flight-pattern leaves no concrete evidence that it took place.
A Resonance of Emerald (3)
This is where the speaker begins trying to describe what she just saw. Rather than just giving us a line like, "I remember it was green," the speaker describes what she saw and what effect it had on her at the very same time. The color is not just something seen, it resonates at a deeper level with the speaker.
A Rush of Cochineal (4)
Here the speaker highlights two reasons she is so awestruck—the bird's speed and its particular color. The word "Rush" also gives a sense of speed, as it's got an onomatopoeia thing going on. "Rush" is a great way to describe the sound of a hummingbird flitting through a flower bush.