UITabbarController in Xcode 8 shows a blue rectangle inside a storyboard view
Edit:
This bug will be fixed in the next release of Xcode 8.2, make sure to update. Xcode 8.2 Release Notes
Ok, so I found out how to remove the blue rectangle.
If I add an image to the button of the tab bar the rectangle will disappear.
And The end result:
just set images to each tab bar in every view controller. and this bug will go automatically. in my case this was the solution.