Yeah, unicorn magic's ALWAYS got a glow! It's different colors for different people - oh, except when they're doing something like really REALLY mega-stupendously magical, then it turns white! I dunno if EVERY unicorn can do that, though, I've mostly just seen Twilights do it and she's the strongest unicorn pretty much ever!

...oh, and I guess sometimes evil amulets can turn it red. But some unicorns just have red magic normally! And that's okay!