Gas discharge lamps have no filament and they produce light in the way that the atoms or molecules of the gas inside a sealed glass, quartz tube are ionized by an huge electric current travel between opposing poles. The color of the lamp depends on many factors: mixture of gasses, other materials inside the tube, the pressure, type and amount of the electric current, etc.  
He, Ne,H and N discharge tubes are four frequently used source in physical lab. This lamp integrates four tubes in one lamp cover.
Suitable choice for physics education in university, removing trouble of changing lamp.