I ran a Google Image search and it appears that any image associated with the phrase "cobalt blue zebra" is listed as a search result, whether it shows an actual CBZ or not (image results included many solid blue CBZ's as well as lot of non-CBZ's such as demasoni's other zebra species, and even some haps and peacocks!, now that's nonsense). Some old photos of mine were among the search results were of ared zebra, and a demasoni with some yellow labs.
"ZEBRA's" are named as such because the very first discovered specimens were of the striped variety. At one time classified as "Pseudotropheus zebra". They were since catergorized various species within the Metriaclima (or alternatively, Mayandia) genus and members of the this genus are grouped into the 'zebra complex' of mbuna's whether they are striped or not.
According to Ad Konings on his cichlidpress.com website, there are at least 20 variants of M. callainos and there's a photo of each of the variants and all of the m. callainos variants are either solidy colored (not necessarily blue) or blotched, none are striped.
For additional reference:
Species Profiles -- Cichlid-Forum
Metriaclima callainos
Malawi Cichlids, Malawi Species Profiles, African Cichlids, Lake Malawi, Malawi Forum, Tanks, Articles, Books, Videos
Maylandia callainos