fix count demo

Samples/UIWidgetsSamples_2019_4/Assets/CountDemo.unity

   m_GameObject: {fileID: 1777874940}
   m_Enabled: 1
   m_EditorHideFlags: 0
-  m_Script: {fileID: 11500000, guid: bb0c6b34bc87472499dccfb52a9bcbde, type: 3}
+  m_Script: {fileID: 11500000, guid: 169ec79ce040653478e1a7725f34bbe1, type: 3}
-  m_RaycastTarget: 1
+  m_RaycastTarget: 0
   m_Maskable: 1
   m_OnCullStateChanged:
     m_PersistentCalls:

Samples/UIWidgetsSamples_2019_4/Assets/Script/CountTest.cs

             public override Widget build(BuildContext context)
             {
                 return new Container(
-                    color: Color.black,
+                    color: Color.fromARGB(255, 255, 0, 0),
                     child: new Column(
                         children: new List<Widget>
                         {
                                 },
                                 child: new Container(
                                     padding: EdgeInsets.symmetric(20, 20),
-                                    color: counter % 2 == 0 ? Color.white : Color.black,
+                                    color: counter % 2 == 0 ? Color.fromARGB(255, 0, 255, 0) : Color.fromARGB(255, 0, 0, 255),
                                     child: new Text("Click Me",
                                         style: new TextStyle(fontFamily: "racher", fontWeight: FontWeight.w100))
                                 )