In high school physics,we built an economy version of the plasma lamps you see in stores like Spencer's. The bulb was a burned out 300 watt clear bulb,the base being one contact,a piece of foil glued to the top(with a thin layer of silicone caulk)the other. A simple HV circuit made from an ignition coil drove it, and the results were not as good as a commercial one, but interesting just the same. Colors,obviously,depended on the gasses in the bulb. It's worth trying,and makes a neat Halloween display.
