Why does Redmi 1 1 SMS notification have a black background?

Black mode. Redmi 1 1 SMS notifies the black background because the default setting is black mode. Background, Chinese words, scenery used to set off the foreground in a stage or movie. Set off the scenery of the main things in pictures and photography. An objective situation that plays an important role in people and things: historical background. Refers to some kind of power behind it: there is often a background behind the underworld.