After attending DEFCON in 2019 I decided to make a RGB LED badge of my own.
The RGB LEDs are APA102-2020. I chose them because they are smaller than the other options and they communicate over SPI which makes it so you can use a standard uC SPI peripheral for control instead of bit-banging a GPIO line.
Check out the below github link for the KiCAD board design files.
The PCB Layout for the STM32-F4 is all on the top side of the PCB. The schematic and BOM are partly borrowed from the Discovery Board design for the STM32 power, crystal oscillator, and the other basic parts needed for the STM32 to run.