Angularfire three-way binding

index.js

// Register firebase module                                                                                         
var app = angular.module("app", ["firebase"]);

// Set up controller function                                                                                       
app.controller("Ctrl", function($scope, $firebase) {
    var firebaseRef = new Firebase(
      // Replace this fictional URL with your own
      "https://burning-limbo-6666.firebaseio.com/colors"                                                          
    );
    // create an AngularFire ref to the data                                                                        
    var sync = $firebase(firebaseRef);

    // pull the data into a local model                                                                             
    var syncObject = sync.$asObject();

    // sync the object with three-way data binding                                                                  
    syncObject.$bindTo($scope, "data");
});