once i connected a incandescent lamp with a broken filament to a microwave oven transformer,the result was a very bright orange flash,followed by a continuous bright blue/purple glow,afterwards when the lamp was turned off because of the high current the tungsten from both ends of the filament was sputtered viloently,blackening the bulb,and causing the removal of the internal coating,i hope to try this experiment whem my philips halogena lamp goes out,the results should be intresting,but not as destructive because the arc is contained in the quartz preventing it from wandering around and melting the outter bulb.

Never heard of that!

the high voltage will ionize the gas filling,and cause a brilliantly colored arc,depending on the type of gas.

Most Incan bulbs now have argon or krypton fill. I have connected 40w bulbs to flyback transformers and gotten a brilliant purpl/blue lightning pattern from it.

The bright light come from the ends acting as discharge electrodes at that moment. The high voltage of the discharge heats them up so they reach thermionic emission, what means for bare tungsten really high temperatures, hence the bright glow.
Then the bluish light is the discharge in the gas fill (on 120V it is almost exclusively Ar or KR, with 230V it means their mixture with N for increased breakdown voltages necessary for the 230V)

If you continue running the transformer the bulb will get sputtered because of the tungsten.