Bumblebee/Cliffjumper
The infamous Bumblebee and Cliffjumper color reversals. All I need is a Bumblejumper pic now. I believe there is some other weird color variations, and I know the Argentinean Transformers have 6 or so different colors for each. All I can say is that Photoshop kicks ass. Instead of painfully redrawing and editing, Photoshop does it for you in less than a minute. Its interesting to see the first series of mini cars has a right to left gradient for the background rather than the customary up to down.
Credits
Base Tech images: Cliffjumper/Bumblebee Tech Specs from the International Transformer Tech Spec Archive