Update @ 2012-08-02: If you are using XCode 4.3 or above. You could following the instruction provided by S.Littlehales.

I found that if u set an image to the UIBarButtomItem directly, only the shape of the image is shown in the view without any color. If you want to add an button image to UIBarButtonItem, you have to create a UIButton and set it to the view of the UIBarButtonItem.
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