No Im talking about having the gas in the tube be from a superheavy element so that when the electron jumps from an energy level it gives off radiation that isnt in the visible spectrum.
discharge tubes are not fully 100% vacuums, by the way most or all of our CRT tubes at school have leaked (does that mean there's holes in the glass or sumthing for it to leak)
also the pressure of the gas. changes the colour. as a different pressure creates a different amount of average collisions per second between the fired electrons and the gas atoms.