All things that were black before, including text, are suddenly gray and I can't find a way to return it to black and white from gray and white. I have booted it twice (held down the power button until it restarted) and it remains gray and white. Bolding to max has helped but it is gray bold and not black bold. Help? Battery was at 35% when this happened, and I may have inadvertently held down the power button for a short time as I was reading. This graying includes the screen when the device is off.