Can animate CALayer alpha, but not backgroundColor

I would like to animate the background color of the layer. I can animate the alpha, but I cannot animate the background color.

Works:

var animation = CABasicAnimation(keyPath: "opacity")
animation.toValue = 0.6
animation.duration = 0.1
customCALayer.addAnimation(animation, forKey: nil)

      

        
        
        
      

    

Doesn't work (no animation, no errors):

var animation = CABasicAnimation(keyPath: "backgroundColor")
animation.fromValue = UIColor.redColor().CGColor
animation.toValue   = UIColor.whiteColor().CGColor
animation.duration = 0.1
customCALayer.addAnimation(animation, forKey: nil)

      

        
        
        
      

    

What's the deal? backgroundColor

is an animated property .

I have read several posts about this and do not understand what I am missing. The lack of feedback for the noop animation is challenging, I'm not sure where it goes wrong. I have tried casting on AnyObject

using NSValue

as a wrapper and I am not getting anywhere.

Similar answers (which didn't work for me):

• stack overflow
• Stackoverflow