Neon gases have a very unique light output, however, their quality of light can diminish over time. Moreover, there is a risk of the capsule exploding. The LED under car lights are much safer in contrast, do not present a significant risk, consume less power to operate, and retain its brightness throughout its lifetime of operation.
Here is how the LED strip light for under body lights work.
They are capable of changing colors.
These LED under car lights are sound active and will flash with the bass of a car. These underbody lights also have a remote included to switch the color pattern.
There is an article on this about LED under car lights on the official iJDMTOY blog.
Also, there are installation instructions on how to properly install your new LED under car lights.