Usually when photographers talk about the green flash, they mean something entirely different from this:
If you happen to be looking, there's about a 30-40 second window where the rooftop lighting of the Frost Bank Tower is just warming up. This makes the roof panels glow green until their color balance gradually stabilizes and they turn white. I always thought it was cool, and it's one of those things I would never have noticed had I not been a timelapse shooter.