When a charged Noise Crush is fired, it is possible to change weapons and "outpace" the color change.
Image below: Roll is using the mega buster, but Noise Crush colors are displayed.
The glitch applies to any weapon, not just the Mega Buster. (I have also seen it with Screw Crusher, for example). I have not performed this glitch (only witnessed it) but I am confident it occurs after firing a charged noise crush.
Also if Noise Crush is charged and the person charging it is fragged, the Noise Crush HUD stays on the screen post-death. (No screen here).