How does the tuning background of red rice note9 turn blue?

Solve it by opening the theme wallpaper of Xiaomi mobile phone and replacing the wallpaper.

Open the homepage of Xiaomi mobile phone theme wallpaper app and click on the official content. Go to the official content page and click on the classic theme. Enter the classic theme page and select the historical theme mode. After clicking download and installation, the volume bar will change from white to blue.

There is another method, the volume adjustment method. Mute means no sound, of course it's gray. Turn off the mute at the bottom and the top will turn blue. Just unmute. This is the volume display. The longer the gray, the smaller the volume. The longer the blue color, the bigger the volume. You can adjust it according to the volume on the side of the phone.