That's the anti-reflective coating, which has a blue tint to it!
One way to see it in action is to put your MagLocks under a lamp. Reflect that light on the front of the lens. Now, flip the sunglasses over and look at the back (blue) side. You'll notice that the light reflected in the lenses is not nearly as bright as the front side.
While it doesn't 100% eliminate reflection, this coating does significantly reduce it– making it clearer to see through the lenses and reducing the eye-strain that occurs from wearing glasses without this anti-glare lens.