Debugging of project is as equal as building it. You need proper tools and means to see whats going on. If it is a field test, you need some sort of visual feedback. Gal Pavlin have built great looking RGB light beepers that are based on STM32F0 microcontroller. They even made a custom 3D printed cap to make it look finished.
The signal light consists of three independent RGB strips controlled by 9 PWM signals generated by STM32F0 microcontroller. LED strips are switched with N-MOSFETs. A separate MOSFET is controlling beeper for audible signal. Microcontroller receives commands from host computer via USB interface which works as virtual serial port. The color depth is 8-bit. The other parameters set by host are color fade time, beep more. For more information refer to GitHub.