Something

package MyRenderers {
    import mx.collections.*;
    import mx.controls.treeClasses.*;

    public class MyTreeItemRenderer extends TreeItemRenderer {
        public function MyTreeItemRenderer() {
            super();
        }
        
        override public function set data(value:Object):void {
            super.data = value;
            if(this.listData) {
            	var myitem:XML = XML(TreeListData(this.listData).item);
            	if(myitem.attribute('name')=='BAR') {
            		setStyle("color", 0xff0000); setStyle('fontWeight', 'bold');
            	}
            	else {
            		setStyle("color", 0x000000); setStyle('fontWeight', 'normal');
            	}
           	}
        }        
    }
}

/*

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
      <mx:XMLList id="myXML">
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="BAR"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>      
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      <node name="FOO"/>
      </mx:XMLList>
      <mx:VBox>
		   <mx:Tree id="tree1" labelField="@name" width="300" height="80" showRoot="true" itemRenderer="MyRenderers.MyTreeItemRenderer" dataProvider="{myXML}" />
      </mx:VBox>
</mx:WindowedApplication>

*/