So; A pegasus other than Rainbow manages to breach the sound barrier, mainly to look cool and add some spectacle to your picture. What should one depict?
Do you make the rings and trail the colors of this other pegasus' mane and coat? Do you make a Rainboom regardless?
Or does one instead play it safe and back down from the whole "Boom" effect entirely and just make a normal "speed lines" trail behind them, thus avoiding ruffling lore feathers, but robbing your picture of some visual spectacle?