I think the Sonic Rainboom should be different colors relating to the mane or color of the Pegasus who did it. Now I myself ask If the Rainboom is an equivalent to a Sonic Boom when you break the sound barrier then could or should there be a move past it for say the speed of light? I mean think about it for a minute, the way it's done, the ring is a perfect example of the shockwave of a Sonic Boom. So if I'm will use Rainbow Dash as an example here. So say she did a Rainboom but keeps speeding up would she turn into like a rainbow color Lightning Bolt like on her cutie mark at a certain speed? But then again that's just my ever curious mind at work.