EmberJS - object proxying is deprecated - accessing property of a controller in template

I'm trying to understand certain peculiarity.

Setting xxx property and iterating #each in one controller works, while seemingly same operation with yyy #each doesn't...

I'm including highlights of the code and the runnable code snippet:

---

App.IndexController = Ember.Controller.extend({
  xxx : [{name:"a"}, {name:"b"}], // this works just fine
});  

{{#each item in xxx}}
  <li>{{item.name}}</li>
{{/each}}

---

App.ColorController = Ember.Controller.extend({
  yyy : [{name:"c"}, {name:"d"}], // this triggers deprecation
  // You attempted to access `yyy` from ...
  // But object proxying is deprecated. Please use `model.yyy` instead
});

{{#each item in yyy}}
  <li>{{item.name}}</li>
{{/each}}

App = Ember.Application.create();
    
    App.Router.map(function() {
      this.resource('color', function(){
        this.route('show', { path: ':color_id' });
      });
    });

    App.IndexRoute = Ember.Route.extend({
      
      model: function() {
        return [
                { id: 1, name: "Red" },
                { id: 2, name: "Blue" },
               ];
      }
    });   

    App.IndexController = Ember.Controller.extend({
      xxx : [{name:"a"}, {name:"b"}], // this works just fine
    });     

    App.ColorController = Ember.Controller.extend({
      init : function() {
        this._super();
        console.info("Just to double check, this controller gets initialised");
      },
      yyy : [{name:"c"}, {name:"d"}], // this triggers deprecation
      // You attempted to access `yyy` from ...
      // But object proxying is deprecated. Please use `model.yyy` instead
    });

  <script type="text/x-handlebars">
    <h2>Ember Starter Kit</h2>
    {{outlet}}
  </script>
 
  <script type="text/x-handlebars" id="index">
    <h3>Index</h3>
    <ul>
      {{#each color in model}}
        <li>{{#link-to "color.show" color}} {{color.name}} {{/link-to}}</li>
      {{/each}}
    </ul>
    <ul>
      {{#each item in xxx}}
        <li>{{item.name}}</li>
      {{/each}}
    </ul>
   </script>

  <script type="text/x-handlebars" id="color/show">
    <h3>color/show</h3>
    <h4>{{ model.name }}</h4>
    <ul>
      {{#each item in yyy}}
        <li>{{item.name}}</li>
      {{/each}}
    </ul>
    {{#link-to "application"}}Go back to the list{{/link-to}}
  </script>
 
  <script src="http://ift.tt/1Ar4Xrj"></script>
  <script src="http://ift.tt/1Iq6rj2"></script>
  <script src="http://ift.tt/1exfLuj"></script>

---

I'd like to learn more:

• why it works in one case and doesn't work in another?
• what is the Ember way of fixing it?