A quick search on cichlidae.com shows a Petrotilapia tridentiger which is a mostly blue fish so it's possible the fish you pictured is a different species or is mislabeled. I don't see any fish listed as P. tritentiger as a valid species. Hopefully someone else will respond.
The main thing you need to know about Petrotilapia is that they get large (6-7'+), and require large tanks (100g+). I kept them in a 150g mixed Mbuna community many years ago, but had to re-home them because they wanted the whole tank to themselves. That said, if it's just the coloration of these fishes that you find attractive, you can get similarly colored fishes in a (somewhat) smaller, (somewhat) less aggressive package in the genus Tropheops, such as Tropheops sp. 'Chilumba,' shown below. Good luck.