The gas helium is a colorless gas, which is not interesting at all to display. One could equally well display a bottle full of air. The inert gas helium, however, is quite interesting, when used in a gas discharge tube at low pressure. When a high voltage is applied to a tube, filled with helium at low pressure, then a current flows and light of a nice orange/salmon color is produced. The picture shows a tube of approximately 20 cm length, which is connected to a 3300 V AC source, in series with a 5 MΩ resistor in order to limit the current.