Do electron tubes that glow blue have a poor vacuum?

The blue glow usually has no direct influence on the vacuum of the tube.

Vacuum dependence: The glow is a function of the anode voltage and the residual gas molecules inside the tube. Even in an excellent vacuum, there are billions of molecules that make this effect possible.

Variability: The intensity varies depending on the individual tube and operating voltage, ranging from barely noticeable to clearly visible even in daylight.

Performance and service life: This blue glow is not a quality defect. Extensive characteristic curve tests confirm that neither the electrical performance nor the life expectancy of the tube is negatively affected by it.