You can force it to sleep by holding the top right button (looks like a TV), then when prompted, select sleep. To Wake it, press the same TV button and it will come back to life.
The sleep setting in General Settings will automatically put it in sleep mode if nothing is actively streaming content. If you turn it off, the white light will remain lit unless\until you force it to sleep.
Flashing white light generally means updates are being applied. If you press and hold Menu + TV for a few seconds, it will reboot, the white light will flash.
Whenever it is active, white light will remain lit. Perfectly normal.