|TL;DR||Look at the File Inspector tab (the one with the blank document) of your storyboard|
Whenever I go looking for the Global Tint defined in the main storyboard in Xcode, there’s always a moment of cognitive dissonance.
My problem is that I go looking for some kind of Window object, which of course is how you’d do it programmatically (in Swift):
UIApplication.sharedApplication().delegate?.window!!.tintColor = UIColor.redColor()
The double !! after window is not a typo according to Xcode, though it sure looks weird.
Anyway, I guess nobody wants to make UIWindows things in Storyboards, so this property is stashed under the File Inspector tab!