Change the color of CheckBox on check or uncheck?

I have a input field type checkbox and I want to change the color on check and uncheck, I tried ng-class = "unChecked =!checked" like this, but not working for me.

Here is my html code:

<input type="checkbox" ng-class = "unChecked =!checked" class="checkbox" ng-model="inventory.productName" ng-checked='true' ng-true-value="true" ng-false-value="false" ng-click="inventory.addRemoveColumn(inventory.productName,'productInfo.productName', 'PRODUCT NAME')" />Product Name
                <br/>

Please tell me how can I do this?