If they are being promoted, let's be able to buy them. A vendor could offer hundreds of colors but if only black or white is available, what's the point?
I recently read that the 'rose' (i.e. copper ed.) was a UK exclusive for the time being, and that as far as Electric Blue, that was a Best Buy exclsuive on the S4 model. No news I've come across on Blue being released by any domestic carrier as of yet. Everyone has charcoal or white as a choice. I would assume that future color releases will come, usually when a competitve device is announced, or a new quarter comes up to boost sales. Seems to be that way in the past.
