The green "neon" lamps are actually argon glow lamps with green phosphor. I saw the spectrum of these green neon lamps and all that i found is the emission of the phosphor. Argon is the best noble gas to produce uv light at normal conditions (Negative glow), and xenon produce enough uv light only in high voltage (Xenon flash lamps) or high pressure (XBO short arc xenon lamps).
That is totally correct that they are argon lamps with the phosphor. they also available in other colors. I also have a bare argon lamp that gives off purplish glow!