Sell more choice / options when it comes to colour.
Being forced to buy a mixed white and black pack or all white packs means I miss out on the savings. I wanted to buy all black as they match my home better but I'd have to by the black individual and lose out on the multi buy savings or buy multiple packs of the white/black combination.
Equally you could sell the button and then buy the covers separately and make them a user changeable component. I'd love to be able to send a colour code and get a custom skin colour back. Anything to make them fit in to the background better or make them stand out more! Point is we'd be able to choose.