Turning off pixels for true black on Note 4

I do a bit of android development here and there and recently got an idea. When charging the note 4 while it's powered off, you may be familiar with how the pixels are turned off except for the the green bubbles. So recently I was playing with themer, and found a bug where I can swap and delete the wallpapers and it leaves the background as a true black (all pixels turned off except icons/widgets).

I was wondering if any of you knew what this is called, like if it has a technical name or something? (the pixels being off)