We can change the theme on the Xiaomi device and customize it to our liking. In addition to the start and lock screens, the system with the icons is also customized. By default, we find two themes to choose from, "Classic" and "Limitless". If we change a theme, we can decide whether the above points should be customized.

Note: The background of the start and lock screen can still be changed.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Themes
Step 3:  Choose a  theme  or tap on  My themes
Step 4:  Choose a  theme
Step 5:  Set  Lock / Home screen, System  or  Icons
Step 6:  Tap on  Apply
  1. Open the Settings
  2. Tap on Themes
  3. Choose a theme or tap on My themes
  4. Choose a theme
  5. Set Lock / Home screen, System or Icons
  6. Tap on Apply

Xiaomi Instructions