public void setBackgroundColors(ColorRGBA clr) {
        if( environment.getVRViewManager() == null ) {
            application.getViewPort().setBackgroundColor(clr);
        } else if( environment.getVRViewManager().getLeftViewPort() != null ) {
            environment.getVRViewManager().getLeftViewPort().setBackgroundColor(clr);

            if( environment.getVRViewManager().getRightViewPort() != null ){
                environment.getVRViewManager().getRightViewPort().setBackgroundColor(clr);
            }
        }
    }
Set the background color for both left and right view ports.
@param clr the background color.
jme3-vr/src/main/java/com/jme3/app/VRAppState.java