I noticed about 20 minutes ago that one of my Power Tubes was glowing both Orange and Blue! Every time before it's been just Orange.
I haven't noticed any difference in sound. So I guess it's every thing's fine.
its telling you to go digital.
If you look through the airvent in the top of my Fireball, you can see red LED's behind the tubes
It doesn't necessarily mean anything. My KT88's glow blue and orange, and they're brand new factory VHT equipment.