How are the colors in neon signs changed?

The color of the light depends on the gas in the tube. Neon lights were named for neon, a noble gas which gives off a popular orange light, but other gases and chemicals are used to produce other colors, such as hydrogen (red), helium (yellow), carbon dioxide (white), and mercury (blue).

Explanation:

those are all the color signs i know this because i did it before

Neon lights don't actually change colors.

Explanation:

Neon signs give the illusion of changing color by turning different components of the signs on or off.