How to make background translucent in iOS 7?

My wife has an iPhone 4s with iOS 7, and when she presses and holds the home button to invoke siri, the siri background is like a translucent blueish color. My iPhone 4s siri screen is black with white text. I've tried setting the home and lock screens with different wallpapers, and also tried using photos for the background. But still my siri background screen is black.

How do I get the translucent background on my siri screen?

-Thanks