He is not a black Kamfa. The black color you were seeing was him being stressed. Now he is settling in and his true colors are beginning to show. If those black colors come back you could add a light colored substrate/stone. Your tank has a lot of black. Both on the divider, and on your tanks background. This can often make flowerhorns turn gray or black. I have a black painted background on my tank, but I use river rock that is different tan colors to brighten the environment and help the colors of my Flowerhorn.