Folders on the LG device's home screen have a white, slightly transparent background by default. The folder color can be adjusted to 11 other colors in the options. Unfortunately, you can't choose your own color for the LG.

Android 9 | LG UX 9.0
Change folder color -  Open desired  Folder
Change folder color -  Tap on  Folder name
Change folder color -  Choose desired  Color
Change folder color -  Confirm with  OK
  1. Open desired Folder
  2. Tap on Folder name
  3. Choose desired Color
  4. Confirm with OK

LG Instructions