Background color should be preserved and set by pvsm infrastructure
Usecase: user creates a visualization in ParaView, setting the background color by any mechanism in the ParaView GUI. The user saves the ParaView state. The user restarts ParaView, switches computers, or otherwise uses ParaView. The user then loads the saved state file. The background color that was in the original visualization should be recreated in the renderview(s) of the loaded ParaView state.
To upload designs, you'll need to enable LFS and have admin enable hashed storage. More information