One of the things I came across in the book was about how the Windows XP visual design team wanted to keep their final design secret. This kept any competing operating system from copying the new look before XP was released.
To accomplish this they created a decoy visual style called Mallard. This was an internal name, and it was commonly known as watercolor. They kept the real theme (Named Luna) secret up until the last minute. I did some searching and found an old screen shot of it:(Click to see it full screen)

Actually I kind of like it. I wish you could still install it, but as far as I can tell you can only get your hands on it by hacking old beta copies of XP.
Posted By: Steve Wiseman on Saturday, April 07, 2007
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