MenuBar:

- use derived colors for menu bar hover
- use derived colors for menu item selected background
- top-level JMenu now uses foreground color from parent JMenuBar

This allows changing menu bar background to dark with:
  UIManager.put( "MenuBar.background", Color.DARK_GRAY );
  UIManager.put( "MenuBar.foreground", Color.WHITE );
or
  menuBar.setBackground( Color.DARK_GRAY );
  menuBar.setForeground( Color.WHITE );

(issue #117)

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatMenusTest.java

@@ -16,6 +16,7 @@
 
 package com.formdev.flatlaf.testing;
 
+import java.awt.Color;
 import java.awt.Component;
 import java.awt.Container;
 import java.awt.Dimension;
@@ -23,6 +24,7 @@ import java.awt.Graphics;
 import java.awt.event.*;
 import java.util.function.Supplier;
 import javax.swing.*;
+import javax.swing.plaf.ColorUIResource;
 import com.formdev.flatlaf.FlatLaf;
 import com.formdev.flatlaf.util.UIScale;
 import net.miginfocom.swing.*;
@@ -69,6 +71,13 @@ public class FlatMenusTest
 			FlatLaf.updateUI();
 	}
 
+	private void popupMenubackgroundChanged() {
+		UIManager.put( "PopupMenu.background", popupMenubackgroundCheckBox.isSelected()
+			? new ColorUIResource( Color.yellow )
+			: null );
+		FlatLaf.updateUI();
+	}
+
 	private void showPopupMenuButtonActionPerformed(ActionEvent e) {
 		Component invoker = (Component) e.getSource();
 		PopupMenu popupMenu = new PopupMenu();
@@ -207,6 +216,7 @@ public class FlatMenusTest
 		JButton showPopupMenuButton = new JButton();
 		armedCheckBox = new JCheckBox();
 		underlineCheckBox = new JCheckBox();
+		popupMenubackgroundCheckBox = new JCheckBox();
 
 		//======== this ========
 		setLayout(new MigLayout(
@@ -222,6 +232,7 @@ public class FlatMenusTest
 			"[top]" +
 			"[]" +
 			"[]" +
+			"[]" +
 			"[]"));
 
 		//---- menuBarLabel ----
@@ -738,6 +749,11 @@ public class FlatMenusTest
 		underlineCheckBox.addActionListener(e -> underlineChanged());
 		add(underlineCheckBox, "cell 0 4 2 1");
 
+		//---- popupMenubackgroundCheckBox ----
+		popupMenubackgroundCheckBox.setText("yellow popup menu background");
+		popupMenubackgroundCheckBox.addActionListener(e -> popupMenubackgroundChanged());
+		add(popupMenubackgroundCheckBox, "cell 0 5 2 1");
+
 		//---- buttonGroup1 ----
 		ButtonGroup buttonGroup1 = new ButtonGroup();
 		buttonGroup1.add(radioButtonMenuItem5);
@@ -756,6 +772,7 @@ public class FlatMenusTest
 	private JCheckBox accelCheckBox;
 	private JCheckBox armedCheckBox;
 	private JCheckBox underlineCheckBox;
+	private JCheckBox popupMenubackgroundCheckBox;
 	// JFormDesigner - End of variables declaration  //GEN-END:variables
 
 	//---- class PopupMenu ----------------------------------------------------

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatMenusTest.jfd

@@ -1,4 +1,4 @@
-JFDML JFormDesigner: "7.0.1.0.272" Java: "13.0.2" encoding: "UTF-8"
+JFDML JFormDesigner: "7.0.2.0.298" Java: "14" encoding: "UTF-8"
 
 new FormModel {
 	contentType: "form/swing"
@@ -9,7 +9,7 @@ new FormModel {
 		add( new FormContainer( "com.formdev.flatlaf.testing.FlatTestPanel", new FormLayoutManager( class net.miginfocom.swing.MigLayout ) {
 			"$layoutConstraints": "ltr,insets dialog,hidemode 3"
 			"$columnConstraints": "[125][][][][]"
-			"$rowConstraints": "[][top][][][]"
+			"$rowConstraints": "[][top][][][][]"
 		} ) {
 			name: "this"
 			add( new FormComponent( "javax.swing.JLabel" ) {
@@ -561,6 +561,16 @@ new FormModel {
 			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
 				"value": "cell 0 4 2 1"
 			} )
+			add( new FormComponent( "javax.swing.JCheckBox" ) {
+				name: "popupMenubackgroundCheckBox"
+				"text": "yellow popup menu background"
+				auxiliary() {
+					"JavaCodeGenerator.variableLocal": false
+				}
+				addEvent( new FormEvent( "java.awt.event.ActionListener", "actionPerformed", "popupMenubackgroundChanged", false ) )
+			}, new FormLayoutConstraints( class net.miginfocom.layout.CC ) {
+				"value": "cell 0 5 2 1"
+			} )
 		}, new FormLayoutConstraints( null ) {
 			"location": new java.awt.Point( 0, 0 )
 			"size": new java.awt.Dimension( 790, 380 )