They had dress changes before the performances of the other 2 songs. They already performed other songs in these red outfits before they did Gashin Shoutan. That's why I think that these outfits were just for this concert, and specifically for this song.
The outfits for the event are not really performance outfits, not really suited for quick changes at concerts. And if these are the for this song we can also expect a non standard music video.
We should know soon enough when we get a video preview or the covers.