How do you get Neon Tube colors?

The colors are derived from a mixture of "Rare" gasses and different types of glass tubing. The two most common gases used are neon and argon. Neon gas emits an orange, redish light, while argon emits an intense light colored blue light. 

Glass tubing comes in many colors. Fluorescent powders are used to coat the inside of the glass to change the color. The combination of gasses and tubing are endless. Tubebenders are able to achieve an infinite amount of colors with different combinations of tubing and glass.