The PowerCD is a weird footnote in the history of Apple’s audio products, but I just recently learned in was going to come in two colors, thanks to this support article:
There original strategy had two colors available for both NTSC and PAL. The Gray was for the business and education channels and the Blue for the consumer. The Blue is no longer available. In Apple USA, model HOO14ll/A, which was Blue, changed to H0014LL/B, which is Gray. After the color change, the only difference between the business and consumer channel models were the CDs that come with the PowerCD.