Change fn-stocks to use a different color toolbar.

sky/examples/fn/widgets/toolbar.dart

 part of widgets;
 
 class Toolbar extends Component {
 
   List<Node> children;
 
   static Style _style = new Style('''
     display: flex;
     align-items: center;
     height: 84px;
     z-index: 1;
-    background-color: #3F51B5;
+    background-color: #9C27B0; // Purple 500
     color: white;
     box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23);'''
   );
 
   Toolbar({String key, this.children}) : super(key: key);
 
   Node render() {
     return new Container(
       style: _style,
       children: children
     );
   }
 }