Female kenyi are purple. Males are yellowish. Demasoni don't exactly "get along" with any mbuna, not even each other. They're like a gang of hoodlums all hopped up on speed. Don't get me wrong, they're stunningly beautiful, but they are not community fish by any standard.
They have a tendency to display the least aggression toward mbuna that do not resemble them. In my tank, I have electric yellows, red zebras, bumblebees, demasoni, and one little punk of a female kenyi. This combination works for me, but as I said before, I would not recommend mixing demasoni and kenyi under any normal circumstances. I only did it because my female kenyi is so aggressive she used to not let any of the other fish eat. I used to have to net her when I was feeding them.
The most appropriate tankmates for demasoni are red, yellow, or white mbuna. Mind you, this does not guarantee that the demasoni will not still kill some or all of these fish. Some demasoni are just an unholy level of aggressive. Some are a little more laid back, and will have minor scuffles with tankmates, but nothing violent. A lot just depends on the individual personalities of the fish.
It helps A LOT to get them as very young juveniles. Mine were only about an inch when I got them, so they pretty much grew up with their tankmates. It also helps to have a serious amount of rockscape in the tank. When you think you have enough cave-like crevices, add at least ten more.