I made the case out of Walnut. I cut the sign front out of Curly Maple on my CNC.  I then placed white acrylic behind it to defuse the RGB LEDs

I control the RGB LEDs via an ESP32 and three N-Channel MOSFETs. The ESP32 is running code to emulate a Philips Hue Bridge with an Extended Color Light. This allows Amazon Echo to discover and control the sign as if it was a Philips Extended Color Light with full support for colors and brightness. It also supports color temperature, but instead of having the sign show different shades of white, I chose to have the color temperature implement animation patterns. For example 'warm white' will cause the On Air Sign to play a rainbow pattern by cycling through all the colors.

What really makes this project awesome is how it automatically turns on when I join a virtual meeting. This magic happens because of the companion software I wrote in C# that runs on my PC to detect a Zoom, WebEx, Discord, and MicrosoftTeams Meeting by monitoring UDP traffic. This application automatically turns on the sign when I join a virtual meeting and turns the sign off when I leave the meeting. 

This sign provides a nice visual clue to my family that I am in a meeting WITH MY VIDEO CAMERA ON, so don't embarrass yourself.    

Below are all the videos that I have created to explain each part of this project in greater detail. 

How to Write an Application to Detect a Zoom Meeting to Automatically turn on Sign

Coding Alexa Support for ESP32 (Arduino)

Alexa Voice Control for ESP32 (Arduino) by Emulating Philips Hue Light

Woodworking | How to Build an On Air Sign case out of Walnut and Maple.

This video shows my full build process for making the sign.

Here is a playlist of all the videos:  My On Air Sign Project Playlist