I started with an off-the-shelf ON AIR sign, that just plugs into a 12V power supply

If you open up the sign you'll see a little holder for two lamps, it's pretty basic!

I removed the lamps

And cut some RGBW NeoPixel strip I had handy

I decided to go with two strips of 30 LED/meter

Some thin wires connect the two strips

Some foam tape or packing tape can be used to keep the strips in place. Solder the strip wires to the Feather, the Power pin goes to USB, Ground to Ground, and Data to #12

I plugged in a USB wall adapter with a MicroUSB plug to power it. You can also go with a long USB cable, that way you could plug it into a USB port and also reprogram it when necessary

Plug it in and rock out!