"Ah," Sirius tries to hide his smile and fails. "Yes, well, Remus was always a bit of a show-off, and loved being dramatic. We figured out how to conjure fire and hold it in our hands without burning ourselves fairly easily—it’s not the hardest thing to do, although  lumos  is a basic spell so no one really tries much except egotistical schoolboys—anyway, Remus learned how to turn his fire green, and would do it constantly to hold it over our heads that we couldn’t figure it out. Thought it made him look cool, I wager, or maybe he just enjoyed being better than Prongs and I at something." 