From what I have managed to find out, through many hours of reasearching them....
If you look in some early publications you will see the melanochromis johanni pictured as what you have, but with the blue being somewhat darker in appearance and with the vertical barring being very clear. One such book (African Cichlids of Lake Malawi and Tanganyika, by Axelrod and Burgess, fifth edition p238) describes them as a Likoma Island morph.
and they are described as being different to what we now accept as a Johanni.
So they have been found in the lake. Are they a cross between a johanni/zebra? If they are a hybrid, it does occour in the lake. Does this make them a species? The same publication does not show the Interuptus, so have they been renamed? Is that in fact what they are. I'm buggered if I know, but what I do know is that they are not accepted as a Johanni by the majority of keepers. Importers and retailers do accept them. I have been watching a pair of these colour up in our lfs and they have very clear vertical barring. Is this a classic example of indecision of species or african miss-identification? Who knows, you make your call! They are still beautiful fish so enjoy them.
Sorry to ramble on but, this is just my own thoughts.
Anyhow welcome to the minefield of african keeping!