A bright ignition phase blossoms outward as it gains altitude. The boost phase involves the spinning control vanes to produce the pretty spirals. The spirals are produced by the early morning light passing through ice crystals that reflect light brilliantly high up in the atmosphere. They report greenish blue light at the center of the spiral at some point. Remember, it's still nearly dark on the ground. Water under sunlight always reflects back greenish blue bandwidth light. Evidence the color of the ocean under direct sunlight.
The most telling pictures are the contrails left behind after the missile passes over. Most of the Youtube nonsense vids cut this section out to make this look U a Foolish & ETish.