I think I've read about this a couple of times back in the Zune Software v1 era, when people were digging the DLLs of the application. Then also we had seen some other colors Zune 30 icons but... the icons was the only thing we saw. Microsoft never released these colors. I don't know if this will happen again with this Yellow Zune Flash Memory Player. EDIT: Mystery solved: This is an internal Zune team gift...
EDIT: The Yellow Flash Zune exists
From IStartedSomething :
The Zune software hasn’t been released for very long but I’ve already thrown my usual arsenal of weapons at it in the hope something undisclosed in the source will waive the white flag. Fortunately, I won’t go to sleep empty handed as I’ve discovered a new device color for the Scorpius 4GB/8GB Zune that is not yet available for sale or mentioned anywhere in the marketing materials.
The fifth color is called “Citron” and can be simply described as citrus yellow. When this color will be available, it will bring the total choice of colors to five - pink, red, black, green and yellow. Unlike the other colors however, the squircle touch-pad is filled black instead of the same color.
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The Yellow Flash Zune exists