One of the great benefits of iOS development is that Apple has provided the ability to customize almost any element thus not limiting a designer or developer with a stock look and feel. Just take a look at subtle examples in Twitter for iPhone to the extreme of the Outside Weather app or Starbucks. I am working on a nice size project and one of the requirements is to have the UIActionSheet buttons be a different color than the default gray color. This turned out the be as straightforward as trying to change the look and feel of a tabbar.
::NOTE TO APPLE:: Customizing Tabbars and UIActionSheet buttons should be a lot easier. ::END NOTE::
It took a few hours, but I finally knocked it out. At first glance I figured that each one of the buttons would be an instance of UIButton and I could located them in the view hierarchy and just update the background color either in a delegate method or subclass UIActionSheet and override drawRect:. NEGATIVE.
My next possible approach was to create my own custom view(s) and slap them on the UIActionSheet's main view and send everything else to the back. Granted that has worked for some people and is a totally viable option, but I found it to be a very hacky solution for what I was doing.
After looking up a few questions on StackOverflow it turns out that sometime after iOS 3.1 the subviews in the UIActionSheet are an undocumented class instances of UIThreePartButton.
::BIG DISCLAIMER - YOUR APP WILL PROBABLY GET REJECTED IF YOU SUBMIT WITH THIS TECHNIQUE::
After digging up that little nugget about UIThreePartButton I finally had turned a corner. The next hurdle was trying to find the correct method to use from the UIThreePartButton class to change the background color. Unfortunately, there isn't a backgroundColor property for that. Granted since I am dealing with a class that inherits form UIView I could set the subviews backgroundColor property to [UIColor redColor], but when I did that I didn't get the expected result of a button with a red background. The button became a red tint and the view behind the button was red as well. Obstacle. Looking at the methods/properties that I DID have I went on a little intuition that Apple wasn't using a color, but a stretchable background image for the button. I grabbed the background graphic that I wanted and used - (void) setBackgroundImage:. SUCCESS!!!!!!!
I wasn't quite finished. Background button was what I wanted, but I needed to change the font color from black to white. But wait there isn't a method to set the font. However, UIPushButton inherits from UIThreePartButton so once again going on an educated guess/intution I was able to use setTitleColor:forState: and perfection. Excatly what I wanted and needed. UIActionSheet with red buttons and white font.
Even though I can't submit any app to the AppStore because of the undocumented class working through the exercise was very enlightening in the areas of ui customization, design patterns and general problem solving skills which should always be in the top of a developer's skillset.
I posted my example on github. It was compiled with 4.0 with XCode 4 Preview 3, but XCode 3.x should work. If you run into any problems then let me know.