text: $(document).ready(function(){
   //adding background color using jquery- this is not advisable as this a css function.
      //  $("button#green").click(function(){
    //      $("body").css("background-color", "green");
    //  });
      $("button#green").click(function(){
          $("body").removeClass();
          $("body").addClass("green-background");
  });
      $("button#yellow").click(function(){
          $("body").removeClass();
          $("body").addClass("yellow-background");
      });
      $("button#red").click(function(){
          $("body").removeClass();
          $("body").addClass("red-background");
      });
  });