In Android 4.4 KitKat and 4.5, the backlights have been turned off.
Now, you can turn them back on by hitting the volume up and down keys.
In 4.6 and later, you need to press the power button to power the device back on.
In all other versions, you simply need to hold down the power and volume keys to turn on the back lights.
If you want to turn off the backlit backlights, just hold down power and Volume down for a second.
In some cases, the screen may flash green, indicating the backlighting is off.
If this happens, the device is currently in standby mode.
If the back lighting is on, the volume buttons can be pressed and the back is on.
If not, hold down volume up for a few seconds to activate the brightness.
The backlights can also be turned off in the settings menu by going to General, Battery and Brightness, Power & Reset, and disabling the power switch.