NSAnimation doesn't work with NSTextField colors

Question

I want to set the text color of a NSTextField using an animation and I tried the following code but it doesn't work. It changes the color immediately without animating the color transition. How do I fix it?

public func changeColor(to: NSColor) {
        NSAnimationContext.runAnimationGroup({ (context) in
        context.duration = 1.0
        context.allowsImplicitAnimation = true
        textField.textColor = to
    }, completionHandler: nil)
}