title: SpriteKit Swift make an entire scene darker, then change it back
body: <p>Is there any way to make an entire scene, including all of its children nodes (not just the background color) darker in color? I am looking for an effect similar to that of this code:</p>
  
  <pre><code>node.color = SKColor.blackColor()
  node.colorBlendFactor = 0.25
  </code></pre>
  
  <p>The above code shades the <code>node</code> a darker color, while keeping the original colors (except that those colors are just darker) and detail.
  However, as far as I can tell, this code doesn't work on scenes, it only works on <code>SKSpriteNode</code>. Is there any way to darken a whole scene? The answer could be some sort of filter, a special way of colorizing a scene, or maybe there is just no way. Anything helps!</p>
  
  <p>Thanks</p>