Is this defender color combination only at ATT?

Hi, I found the Puple/Blue Otterbox Defender for iPhone 4s (new design) on the ATT Wireless Accessories website, but really don't want to pay the $50 for it considering the other Defender case I'm buying from Amazon for the 4s is 32 with free prime shipping. Are there certain color combinations that only certain carriers get or is this maybe so new that it hasn't trickled down to any other stores yet?

Also is it true that the inside case and the rubberized outside of the Defender's can be interchanged? Thanks!