title: Libgdx applying color to model instance doesn't work
body: <p>I'm trying to import a obj model to libgdx and apply one color to it - no shading whatsoever, just one color on all faces.</p>
  
  <p>this is what I use in my create method:</p>
  
  <pre><code>    modelBatch = new ModelBatch();
      ObjLoader loader = new ObjLoader();
      model = loader.loadModel(Gdx.files.internal("data/test.obj"));
      model.materials.add( new Material(ColorAttribute.createDiffuse(Color.GREEN)));
      instance = new ModelInstance(model);
  </code></pre>
  
  <p>and in my render method:</p>
  
  <pre><code>    Gdx.gl.glClearColor(52 / 255f, 152 / 255f, 219 / 255f, 1.0f);
      Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
      modelBatch.begin(perspCam);
      modelBatch.render(instance);
      modelBatch.end();
  </code></pre>
  
  <p>The result is that model is white/grayish - why isn't it green?</p>