Sometimes I wonder if Elon's flair for PR makes stuff like this happen or it was just luck? It seemed to be timed so perfectly. From what I understand, the booster fired when the rocket was high enough to catch the last of the sun's rays, which lit up ice crystals that formed when the water in the exhaust froze. And it was backlit over a dramatically dark sky and over city lights and there was still color in the sunset and and and!
This photo came from SmugMug customer Brandon Yoshizawa who went to the mountains to shoot it. Incredible.