The instructions for nerves_system_bbb describe using dd to erase the EMMc memory, so that the beaglebone black will boot directly to the SD card without having to hold down the boot/SD button.
I discovered that the device name for the eMMC on the Blue is mmcblk1, so the command for the Blue is:
sudo dd if=/dev/zero of=/dev/mmcblk1 bs=1M count=100
