@Override
	public Color getBackground() {
		// not storing value of "TitlePane.unifiedBackground" in class to allow changing at runtime
		return (UIManager.getBoolean( "TitlePane.unifiedBackground" ) &&
				clientPropertyColor( rootPane, TITLE_BAR_BACKGROUND, null ) == null)
			? FlatUIUtils.getParentBackground( this )
			: super.getBackground();
	}
Returns whether the menubar should be embedded into the title pane.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTitlePane.java