protected void activeChanged( boolean active ) {
		Color background = clientPropertyColor( rootPane, TITLE_BAR_BACKGROUND, null );
		Color foreground = clientPropertyColor( rootPane, TITLE_BAR_FOREGROUND, null );
		Color titleForeground = foreground;
		if( background == null )
			background = FlatUIUtils.nonUIResource( active ? activeBackground : inactiveBackground );
		if( foreground == null ) {
			foreground = FlatUIUtils.nonUIResource( active ? activeForeground : inactiveForeground );
			titleForeground = (active && hasVisibleEmbeddedMenuBar( rootPane.getJMenuBar() ))
				? FlatUIUtils.nonUIResource( embeddedForeground )
				: foreground;
		}

		setBackground( background );
		titleLabel.setForeground( titleForeground );
		iconifyButton.setForeground( foreground );
		maximizeButton.setForeground( foreground );
		restoreButton.setForeground( foreground );
		closeButton.setForeground( foreground );

		// this is necessary because hover/pressed colors are derived from background color
		// (since FlatWindowAbstractIcon now invokes FlatTitlePane.getBackground()
		//  to get base color, this is no longer necessary, but keep it for compatibility;
		//  e.g. for custom window icons)
		iconifyButton.setBackground( background );
		maximizeButton.setBackground( background );
		restoreButton.setBackground( background );
		closeButton.setBackground( background );
	}
This panel paint a border at the top of the window in fullWindowContent mode,
if FlatLaf window decorations are enabled.
Only used on Windows 10.
<p>
This panel is not a child of the title pane.
Instead it is added by FlatRootPaneUI to the layered pane at a layer over all other layers.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTitlePane.java