在UITableView中定制索引/节栏的字体/背景颜色

I've read in another thread on SO that you can adjust the font or background colour of the index bar (that is the A-Z # scrollbar) in a UITableView adding a CALayer. My app will be running on iOS 5 and above and since I haven't seen anything about this in the Apple docs, would it be right to say that it simply isn't possible without creating a custom table view? I've read in another thread on SO that you can