How can I change the color as well as size of UIProgressBar in iPhone SDK
As Can noted, there is very little customization available for UIProgressView... pretty sucky. The solution I just implemented was to hack a UISlider. Here's the inspiration, from Apple's support forum.
Once this is setup and added to your UIView, use your custom method to set the value of the slider to the value you would normally have assigned to the UIPRogressView's progress.