Is the Xiaomi 6 screen backlight in this position?

Breathing light's location is shown below, in the middle of the bottom of the mobile phone.

Click "Settings"

Click Other Advanced Settings.

Click on "breathing light"

Be sure to turn on the button "The indicator flashes when receiving the notice" so that breathing light will flash when receiving the notice.

As you can see, there are three notification color type settings: notification color, incoming call color and SMS color.

Click the notification type you want to set, and a variety of colors will appear for you to choose from. In order to distinguish general notifications, it is best to set other colors except green and red for notifications, short messages and incoming calls.