User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-11537809-20150116161724/@comment-1921299-20150116225530

From what i can tell the faded glow is from not being angry but still being frenzy.

As the glow re-strengthened after a few hits to the main body and it let out another roar, it had lso stopped huffing virus when the glow went away but it came back after the roar..