NLS - Cichlasoma Formula, Ching Mix, Grand Sumo, Grand Sumo Red, Ionic, etc. There's a ton of different foods. Don't feed into the "this food will build the hump" hype. The coloring also isn't always a guarantee. Genes play the biggest role in your fish. You just want something healthy for the fish, and NLS is usually the best out there. Feed it well, 3 times a day. Keep the tank clean.
I just grabbed the same exact fish, almost identical, from my lfs. $20. It's all a gamble at that stage. Mine's about an inch. They call em blue diamond, thai silk, titanium, and whatever else name they want to give it. It's a Thai Silk nonetheless. Growing it out more is the only way to see if it has true potential, still too small, but has a great blue covering over body and all the way into his fins. I'm sure it will come out great!!