I've been seeing this in 4600 and 4900 tubes lately. it's like a dead heater short on the colors. there's no way to fix it.
the Galaxian at work periodically will flash full red at random, and I would entirely lose colors on the rejuvenator trying to flush it out. it didn't change at all when I was done, so it's just a junk tube. I took a good 4600 and put it in there instead, cause Galaxian deserves better.