ASP.NET MVC 5 calling controller method from Javascript Error

I am attempting to call a controller method from javascript and I seem to be having trouble getting this to execute correctly. I have very little experience with javascript and have followed other examples of how to do this from stackoverflow but I am still having some issues- if anyone can help that'd be fantastic.

Basically what I am trying to do is set a .data tag on a javascript object to the string returned by a method on the controller (this method calls a webservice that runs a SQL Server function). The method needs to be passed one parameter which is used in the function.

The code is below:

Javascript Code

for (var i = 0; i < stats.length; i++)
{ 
    var stat = stats[i].data('id');
    var color = CallService(stat);
    this.node.fill = color;
}

JQuery Method

    function CallService(id) {
    $.ajax({
        url: '@Url.Action("CallService", "NodeController")',
        type: 'GET',
        dataType: 'json',
        cache: false,
        data: { 'id': id },
        success: function (color) {
            return color;
        },
        error: function () {
            alert('Error occured');
        }
    });
} 

Controller Method

    [HttpGet]
    public JsonResult CallService(string id)
    {
        var idNum = Convert.ToInt32(id);
        var StationService = new getStationStatus.Service1SoapClient("Service1Soap");
        string color = StationService.getStationStatus(idNum);
        return Json(color, JsonRequestBehavior.AllowGet);
    }

the controller is called the NodeController- which is what I am referring to in url: call of ajax.

Basically what is happening is when i run the page, I first get an error saying it cannot set this.node.fill to a null value THEN I get the alert that an error occurred- like I said I am pretty inexperienced with javascript so I am honestly not even sure if it is calling the method in the correct order if i get an error on this.node.fill before I receive the error message from JQuery.

Any/all help or suggestions is greatly appreciated!!!