     private var titles: [UIControlState: [PermissionStatus: String]] = [:]
     private var attributedTitles: [UIControlState: [PermissionStatus: NSAttributedString]] = [:]
     private var titleColors: [UIControlState: [PermissionStatus: UIColor]] = [:]
+    private var titleShadowColors: [UIControlState: [PermissionStatus: UIColor]] = [:]
     
     // MARK: - Initialization
     

    /**
    Returns the title color used for a permission status and state.
    
    - parameter status: The permission status.
    - parameter state:  The state.
    
    - returns: The color of the title for the specified permission status and state.
    */

        if let color = titleColorForStatus(status, andState: state) {
            super.setTitleColor(color, forState: state)
        }
        
        if let color = titleShadowColorForStatus(status, andState: state) {
            super.setTitleShadowColor(color, forState: state)
        }
    }
    
    @objc func highlight(button: PermissionButton) {
