title: changing the tree nodes background colour in extjs4
body: <p>I am very new to JS so please forgive me if i am asking very basic question. </p>
  
  <p>I want to change the background colour of the node in the tree i have here.</p>
  
  <pre><code>Ext.application({
              name: 'Autopsy',
              launch: function() {
              Ext.create('Ext.container.Viewport', {
                      layout: 'border',
                      items:[ {
                          ......
                          .......
                      }, {
                          region:'west',
                          collapsible: true,
                          resizable: true,
                          title: 'Threads (Total: {{ num_threads|replace("\n","\\n") }})',
                          width: 200,
                          layout: 'fit',
                          items: [
                              {
  
                                  xtype: 'treepanel',
                                  rootVisible: false,
                                  store: threadStore,
                                  lines: false,
                                  useArrows: true,
                              }
                          ]
                      }, {
                         .....
                         .....
  </code></pre>
  
  <p>ThreadSotre is</p>
  
  <pre><code>          var threadStore = Ext.create('Ext.data.TreeStore', {
                                  root: {
                                      text: 'Root',
                                      expanded: true,
                                      children: [
                                          {% for thread in threadIds %}
                                          { text: "Thread {{ thread }}", leaf:                 true },
                                          {% endfor %}
                                          { text: "Thread Ex", expanded: true, children: [
                                              { text: "funcTop", leaf: true },
                                              { text: "funcBottom", leaf: true},
                                              { text: "test", leaf: true}
                                          ] },
                                      ]
                                  }
                              });
  </code></pre>
  
  <p>this give me an output like below</p>
  
  <p>Thread 6</p>
  
  <p>Thread 5</p>
  
  <p>Thread 4</p>
  
  <p>Thread 3</p>
  
  <p>Thread 2</p>
  
  <p>Thread 1</p>
  
  <p>I want the back ground color of "Thread 1" to be red. How can i do it ?</p>