The difference in shade between them is subtle but there - Firefly tends to be a warm pink, while Twilight edges ever so slightly towards the cool/purple side of pink (by no means purple but if you graphed it, closer than Firefly's pink which is smack dab on red, maybe leaning a bit towards peach/orange tinged pink.) Personally I've always been a fan of paler Twilight, it contrasts nicely with her royal purple stripe and stars.