Sliced bread is a benchmark for inventiveness.
Having performed several searches, as usual, I haven’t yet come up with any prior claims in connection with today’s invention: a loaf consisting of both brown and white slices.
People like variety, so I reckon this is a reasonably healthy way to introduce some novelty and add extra interest to a staple foodstuff. One brown and one white loaf would be sliced in the usual way and interdigitated, like two halves of a pack of cards, resulting in two such mixed loaves.
A more advanced version would have several different types of sliced bread involved. It might even be possible to introduce a toasted image onto some of the slices before ‘zipping’ the bread together to conceal eg a surprise message (and tie this in, perhaps, to some consumer competition).