title: UIButton background color becomes white when running on iOS6
body: <p>I wonder why the buttons of my iPhone app is not displaying properly when running on an iOS 6 device.  I have set the buttons' background color to a blue color in Interface builder. However, when running on iOS 6 the buttons background became white.</p>
  
  <p>This is how the button look like when running on iOS7</p>
  
  <p><img src="https://i.stack.imgur.com/XPF0z.png" alt="enter image description here"></p>
  
  <p>And this is how the buttons look like when running on iOS6</p>
  
  <p><img src="https://i.stack.imgur.com/dllp3.png" alt="enter image description here"></p>