There is a purple glow,would that be xenon? There is only a glow around the outside of the bottom of the mini starter bulb which arcs over to the wire support near the stem, only when lamp is energized hot until re-strike.There is no glow observed when lamp is started cold.
this acts as a voltage buffer, this absorbs the High Pulse Voltage generated from the Ignitor from the arctube until it cools down sufficiently to restrike.
More details at http [at] en.wikipedia.org [slash] wiki [slash] Noble_gas [pound sign] Discharge_color
I think it is to reduce the stress on the arc tube which could explode suddenly with high voltages striking the hot gasses, within the arc tube
Out of interest I have the Same Lamp see HERE
All the Best
Colin