There is no way to configure the native iPad on-screen keyboard in the way that you want - even in iOS5. There were some changes made in iOS5 but not this one, unfortunately. Of course, there are numerous third party keyboards available, but they need to be used within a separate 'keyboard app' and don't replace the stock keyboard.
You can change the color of your keyboard buy going into the settings and inverting the color of your screen. Your keyboard will be black but the downside is all the other colors will be inverted.