The LO vector view should show the background color as setup for the style that is saved with the scene. It won't show ground, sky, or watermarks.If the SU background is set to low or no opacity, Vector view will reflect that. The LO SketchUp model view can also have a color "fill" set in the window "Shape Style". One way that what you describe can happen is if the background color in SU is set to white and transparent. This shows solid white in LO under "raster", but becomes clear under "vector". If the model view has a blue fill per the "Shape Style" window, then you would see that with vector. Unclick the fill and you would remove the blue color.