Neon produces light that is orange-red. Other coloured “neon lights” either contain other gasses, or have tinted glass to produce other colours.
We’ve all seen elaborate logos and illuminated signs, so we know that that neon lights come in a variety of colours. It would seem that the answer to the question is that neon light comes in many different colours, but that’s not really the case.
The light that is generated when an electrical current is applied to Neon gas is orange-red in a low-pressure tube.
What about other colours?
All noble gasses emit light when a charge is applied. Different gasses produce different colours. Different colour light can be generated by substituting or combining other gasses.
One way is to use another gas or a mixture of gases to produce colors. [Each] noble gas releases a characteristic color of light. For example, helium glows pink, krypton is green, and argon is blue. If the gases are mixed, intermediate colors can be produced.
Another method used to produce different coloured light is to colour the glass tube itself. Sciencing explains “Baking fluorescent powders onto the inside walls of the glass tubes also modifies the colors and shades of the finished neon sign. Colored glass tubes are also used for the same effect.”
So why are they called neon lights?
Neon was discovered around the end of the 19th century. By 1910 a French engineer named Georges Claude invented a neon light that resembles what is in use today. It became very popular in the early 20th century. When the lighting technique was later adapted to become the neon lights we know today they never lost that original name even though some of the lights may not contain any neon.