[Amps] tube glowed red when grid resister blew on sb-220

[Dan Sawyer]

All,

Recently one of grid resisters blew on an SB-220. The result was the 
tube glowed deep red to purple. Is this a reasonable outcome for a blown 
grid resistor on an SB-220? If the incident was only a few seconds long 
was the tube damaged??

Thanks,
Dan