Product RED is not exclusively red/white, as evidenced by this product sold in their stores. That is just Apple sticking to what IT thinks is best, regardless of what customers want.
have you considered that this change and product actually wasn't for what Consumers want? i don't recall a huge outcry for red iPhones. if anything it seems a way to maximize the amount of money going to charity.
think about this.
to make a big change in design(even something as little as changing the Color of the Touch ID Ring) they need to pay people to literally design this.
then they need to pay people to build the new red parts (the more parts they change, the more it costs)
then pay more people to build the device with all the new parts (instead of literally switching 1 part in the production process, they'd be added 2-4 new parts)
then they need to stop the production of current devices(wether it be the currently bought 7's, or pull resources away from the 8's/new devices being built at the moment)
all of this normally cuts into their profits, which probably wouldn't be an issue, if the point of the (product)red device wasn't to DONATE those same PROFITS.
so imagine possibly raising 100millions dollars with just changing one piece(back casing) but instead only donating, maybe, 50 million because they went that much further and changed 2-4 pieces(back casing, Front Bezel, Touch ID ring, Back apple logo,*insert any other changes you guys are thinking should have been done*)
i mean, they obviously took the route that maximizes the profits to go to the charity, changing 1 item( back case) and using the white front bezel, the more popular bezel color that that most likely already have a lot of resources producing (3 iPhone models have the white bezel, versus 2 with the black, one of which is a much less popular jet black)