1076 electrical mentor here.
The LEDs are driven by a
Pololu A-Star 32U4 (more or less an Arduino Leonardo). This is connected to the serial output on the RoboRIO's MXP.
When powered on, it runs the idle animation and waits for serial data. Once it receives data, it does a boot-up animation and then the main one (stripes that move back and forth with the motors they're next to). If no data is received for 750 milliseconds, it does a shutdown animation and then back to the idle.
The RoboRIO sends a single byte every time it runs through the control loop during autonomous and teleop to tell it which motors are moving which direction. We aren't actually telling it to run the idle animation, it just falls back to it when there's no data.
If anyone's curious, we're powering the LEDs with one of these
http://www.mini-box.com/DCDC-USB.
We initially bought it for our Jetson TK1, but that didn't end up making it onto the robot this year.