Here\'s my code that creates the UIAlertController
// Create the alert controller
var alertController = UIAlertController(title: \"Are you sure you want
Piyush's answer helped me the most, but here are some tweaks for Swift 3 and to change the title and message separately.
Title:
alert.setValue(NSAttributedString(string: alert.message, attributes: [NSFontAttributeName : UIFont.systemFont(ofSize: 29, weight: UIFontWeightMedium), NSForegroundColorAttributeName : UIColor.red]), forKey: "attributedTitle")
Message:
alert.setValue(NSAttributedString(string: alert.message, attributes: [NSFontAttributeName : UIFont.systemFont(ofSize: 29, weight: UIFontWeightMedium), NSForegroundColorAttributeName : UIColor.red]), forKey: "attributedMessage")
The big font size is because I actually needed to do it for tvOS, works great on it and iOS.