some are:neon-for a strong red glowargon- for a light blue colorhelium- for a pinkish red glowxenon- for a bright lavender glowkrypton- for a yellow- whiteradon- for a yellowish greenish.and many...
The finished sign tube, complete with its electrodes, has a "port" in it where a vacuum pump is attached and all the air in the tube is removed. After the tube is pumped down to remove air, it is...