If you hold the power button and the two volume buttons down for a bit of time the tablet displays an android with a door on the belly open. Options include Start, Restart Bootloader, Recovery Mode, Power Off. Selecting Recovery gets you to a new set of options which include reboot system now, install zip, wipe data/factory reset, wipe cache partition, backup and restore, mounts and storage, and advanced. (Not part of this post but if you pick advanced you get options reboot recovery, reboot to bootloader, power off, wipe dalvik cache, report error, key test, show log.)
Now while in recovery, if you press the two volume buttons for a brief moment the options change from a single color to a bunch of colors. A message gets displayed saying the device is in rainbow mode.
What is rainbow mode and how is it different from being in non rainbow mode?