As follow picture,I want the bubble color auto changed by data,eg:if the value>0 the color red,else the color blue.

I've use follow code to get data,but if I follow like this,all of bubble will red or blue,not like I want just value less than 0.

How can I do to make it realize?Just the value greater than 0 will red,and others blue?

var va=DS_1.getMembers("ZCQYF", 2000);
va.forEach(function(element, index) {
var v=DS_1.getData("OVERDUE_TTL", {"ZCQYF": element.internalKey}).value;
LISTBOX_1.addItem(v+"", v+"");
 if(v>=0){
   LISTBOX_1.setCSSClass("red");
 }else if(v<0){
  LISTBOX_1.setCSSClass("blue");
 }
});