Isn't that neon?...

:lol:

Not necessarily. Neon gas when excited by an electrical discharge produces an orange-red glow within a clear glass discharge tube, which is the basis of our neon lights. Adding green-emitting phosphors to the tube tones the color of the gas down to orange, adding a blue-emitting phosphor results in a hot pink light, a red glass tube will result in a deep red light. In the same situation He gives an orangy-white light, Xe a dim blue-grey, and Kr a dull green discharge. Ar actually gives a dim purple glow, but when it is mixed with Hg vapor, it excites the Hg and produces a brilliant light blue color which can be adjusted to blue-green, pale green, light yellow or purple by varying the phosphor coating or the color of the tubing. That color variation is probably what was meant, but technically, it isn't the Ar but the Hg that is actually being stimulated and giving the discharge glow, though (to be fair) it wouldn't be possible without Ar and Ar-Hg vapor is the basis of much of modern "neon" art. The other gasses are now very much restricted in use because of price and availability. Ar is otherwise used in incandescent bulbs in which the gas (unlike discharge tubes) isn't excited but merely keeps the filament from burning without the trouble of creating a vacuum. It is also used in welding to keep the very hot metals from burning in an atmosphere of O₂. In that case it isn't very exciting at all.

Is that the ion colour/...