title: UIButton background color for highlighted/selected state issue
body: <p>I've a <code>UIButton</code> and I've created an extension to add background color for different state. </p>
  
  <p><strong>I'm using the following code:</strong></p>
  
  <pre><code>extension UIButton {
  
      func setBackgroundColor(color: UIColor, forState: UIControlState) {
  
          UIGraphicsBeginImageContext(CGSize(width: 1, height: 1))
          CGContextSetFillColorWithColor(UIGraphicsGetCurrentContext(), color.CGColor)
          CGContextFillRect(UIGraphicsGetCurrentContext(), CGRect(x: 0, y: 0, width: 1, height: 1))
          let colorImage = UIGraphicsGetImageFromCurrentImageContext()
          UIGraphicsEndImageContext()
  
          self.setBackgroundImage(colorImage, forState: forState)
      }
  }
  
  
  // Set Button Title and background color for different states
      self.donateButton.setBackgroundColor(UIColor.redColor(), forState: .Normal)
      self.donateButton.setTitleColor(UIColor.whiteColor(), forState: .Normal)
      self.donateButton.setBackgroundColor(UIColor.greenColor(), forState: .Highlighted)
      self.donateButton.setTitleColor(UIColor.whiteColor(), forState: .Highlighted)
      self.donateButton.setBackgroundColor(UIColor.greenColor(), forState: .Selected)
      self.donateButton.setTitleColor(UIColor.whiteColor(), forState: .Selected)
  </code></pre>
  
  <blockquote>
    <p>My Problem is that it is not picking up proper <code>UIButton</code> background color and title color for highlighted/selected state.</p>
  </blockquote>
  
  <p><a href="https://i.stack.imgur.com/aFjgX.png" rel="noreferrer"><img src="https://i.stack.imgur.com/aFjgX.png" alt="Normal state"></a>
  <a href="https://i.stack.imgur.com/jPqb2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/jPqb2.png" alt="Highlighted state"></a></p>