public void setBackgroundColors(ColorRGBA clr) {
        if( viewManager == null ) {
            getViewPort().setBackgroundColor(clr);
        } else if( viewManager.getLeftViewPort() != null ) {
            viewManager.getLeftViewPort().setBackgroundColor(clr);
            if( viewManager.getRightViewPort() != null ) viewManager.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/VRApplication.java