First compile the module;
make
Then detech usbhid from the the third interface (could be done with udev rule)
sudo echo 1-3.2:1.2 | sudo tee /sys/bus/usb/drivers/usbhid/unbind
then load the driver
sudo insmod led-class.ko
Now in /sys/class/leds you will see 3 new entries, simply echo a value between 0-255 to the appropriate brightness file, IE for blue (as root)
echo 255 > usb-1-3.2:w:gpd-blue/brightness
TODO see what steps can be removed from the usb write/reads to make faster, and add keyboard remapping