求救！在线等！各位高手，如何根据数值的正负设置颜色

下面是我的代码：怎么根据gdvalue的值设置它显示的颜色
<%@ page contentType="text/html;charset=UTF-8" language="java"%>
<%
 response.setHeader("Pragma","No-cache");
 response.setHeader("Cache-Control","no-cache");
%>
<html>
<head>
<title>股票信息</title>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
<script type="text/javascript" src="/portalExternal/js/jquery.js"
charset="UTF-8"></script>
<script type="text/javascript">
/*获取stock.json里面的股票信息*/
        $(document).ready(function() { 
            $.ajax({
             url:"/portalExternal/stock.json",
             type:"GET",
             dataType:'json',
             success:function(data){              wirteHtml(data);
             },
             error:function(){
              alert("error");
             }
             });
         }); 
            
            
         function wirteHtml(data){
            var htmlstr="";
         $.each(data, function(index,value){ 
         
         var row = $("#template_0").clone();
         row.find("#name").text(value.name);
         row.find("#dvalence").text(value.dvalence);
         row.find("#gdvalue").html(value.gdvalue);
         row.find("#gdrange").text(value.gdrange);
         row.appendTo("#table");
        });  
     }
    </script>
</head>
<body>
<div id="stockMessage" style="overflow: hidden; height: 80px; width:500px; align: left">
<tbody>

    <marquee style="WIDTH: 500px; HEIGHT: 80px" width=400 direction=up scrollamount=2 onmouseover="this.stop()" 
    onmouseout="this.start()" style="padding: 50px 10pt;" >
    <table id="table" width="380" height="50" border="0" cellpadding="0" cellspacing="0">
     <tr id="template_0">
     <td align="center" width="200" id="name"></td>
<td align="center" width="100" id="dvalence"></td>
<td align="center" width="100" id="gdvalue"></td>
<td align="center" width="100" id="gdrange"></td> 
</tr>
  </table>
</marquee>
</tbody>
</div>
</body>
</html>