Following this tutorial, I made this awesome monitor backlight that follows the average color of your screen at any time. It uses an Arduino, a few transistors, and some RGP LEDs. I made changes to the code to calibrate my lights to more accurately reflect the color of my screen, and also added the ability to just display a constant color of your choice. As someone who gets migraines from light sensitivity, I really enjoyed having this smooth out the lighting while staring at my monitor.