How are the colors in neon signs changed?

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.

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

a plasma is a warm ionized gasoline consisting of approximately equal numbers of definitely charged ions and negatively charged electrons. the characteristics of plasmas are notably unique from the ones of ordinary neutral gases in order that plasmas are considered a awesome "fourth kingdom of remember."

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.