Update: This appears to be working in the beta of IOS 4.3!
One of the things that is broken in iOS 4.2 is the tint color on the navigation bar in the Root View of the SplitViewController. What happens is that if you set the tint color, it will show correctly until you rotate to portrait mode, tap the List button, then rotate back to landscape.
The issue is discussed in great detail here: https://devforums.apple.com/thread/68443?start=0&tstart=0
One of the proposed solutions is to SubClass the NavigationBar Class and override the setTint method. (Credit goes to Hans Harris)
Below is a link to a complete working implementation.