It's a play on Remilia's "Red Magic" spellcard. Clever...
...and then if I take this towel off...Uuuuh!!! Make fun of me, will you?!!! I absolutely won't allow it!!!I saw them!I'll finish you bastards off and blow you away!!!YES!!Dangle...it's somehow a red bullet!! Isn't it amazing...?*clap*
*clap*Oooh...Ummmm... I'll take this white bullet* and cover it with this towel...
*One of the individual bullets in danmaku