The color of the lock icon shown when an app is not allowed to access to photo or calendar in iOS 8

EKEventEditViewController shows the lock icon when an app doesn’t be allowed to access to the device’s calendar. Our app running on iOS 7 displays a gray lock icon. But on iOS 8, a black icon appears instead.

Is it only a design change in iOS 8 update? Or is there something wrong with our app?

I found a same black icon at an photo selector screen in another app.