"Lamps of this kind are made in every possible shape, in various lengths and many colours. The glass tube can be shaped as desired and is also available in various colours.
Glass tube: 9-35mm external diameter and up to 3m long, wall thickness
Glass: Coulorless glass tube, suitable for all luminous colours
Filter glass: In yellow, blue, red, transparent; suitable for green, blue-violet, red and yellow luminous colours
Luminous substances: More than 40 different luminous colours "
From Light Fantastic by Max Keller