I hope they bring back the Black Macbook.
My guess is just make the plastic white MacBook silver in colour (plastic).
OLED in iMac? Puuuuull-eze! It's not even available in the iPhone and *it* has a much smaller screen. The PP who said a more energy efficient processor being an energy saver and thereby a money saver, is probably more right.
Now that said, it would be quite embarrassing for Apple if Microsoft releases a Windows 7 OLED (touch) screen. They already been have been spanked by the Zune HD with a OLED.