Steve,
A bit or swirling of color as a regulator tube lights off is not
uncommon. Until the tube is in full operation and the circuit being
supplied stabilizes, the state of the gas will vary. The tube will also
"swirl" if the current is changing, as in keying up a transmitter. If,
however, the regulator tube has a defined, white flashing or arcing,
then you do have a problem. Typically, a "light-show" coming from a gas
voltage regulator in a properly designed and operating circuit indicates
a failing tube. In any case, you might want to measure the voltage
applied to the regulator tube at the time it flashes on you.
Solid-state power supplies provide B+ almost instantaneously, well in
advance of the tube circuits heating up in your receiver. It may be
that a temporary, excessive voltage is being applied to the regulator
tube, in advance of the circuit(s) being supplied are drawing current.
If that's the situation, measure the series dropping resistor's value as
it could have changed over time, downwards. Hope this adds something
towards answering your question.

de Jeep/K3HVG

Steven L Umbach wrote:
My Drake R-4B works fine but sometimes when I turn it on the OB2 tube puts
on a light show with swirling orange glow brightening up the inside of the
radio. It was kind of scary the first time I saw it. Usually when it does
that if I turn it off once or twice it stops doing that. Is this a cause for
concern? Is the tube going bad or indication of some other problem? I don't
have a spare of that tube on hand but I can get one on Ebay for not much.
Thanks.

Steve