I have the following html: 

```
<button id="simpleBtn" data-bind="jqButton: true, click: runTest, style: {backgroundColor: color}">Click me</button>

```

and the following model:

```
function Test(testName, test) {
            var vm = {};

            vm.result = ko.observable(false);
            vm.testName = testName;
            vm.color = ko.computed(function (){
                return vm.result() === true ? 'green' : 'red';
            }, vm);

            vm.test = test;
            vm.runTest = function () {
                var result = vm.test();
                vm.result(result);
            }

            return vm;
        }

        ko.bindingHandlers.jqButton = {
            init: function (element) {
                $(element).button();
            }
        }

        ko.applyBindings(Test('Name', function () {
            //test code
        }));

```

I want to change the style of button, but this code doesn't work. What should I do to make it work?