By default, the colour of the control bar on the LG device is set to white. The colour can be changed to pale paste colours. Unfortunately, it is not possible to select your own colour for the navigation bar.

Android 9 | LG UX 9.0
Step 1:  Open the  Settings
Step 2:  Tap on  Display
Step 3:  Tap on  Home touch buttons
Step 4:  Tap on desired  Color
  1. Open the Settings
  2. Tap on Display
  3. Tap on Home touch buttons
  4. Tap on desired Color

LG Instructions