For a Dempsey? A good staple diet would be to combine a mixture of the red/green hikari cichlid pellets. Choose an appropriate size, make sure it's not too big. It might take him a few days to take the pellets, but if you have to starve him, he will be ok. Another treat that you can keep on hand is freeze-dried krill, he should like it alot. Don't let him get too used to it though, as he will become spoiled and refuse pellets.
There is a ton of treats you can feed your fish, but if you make them a staple, you will go poor. Such alternatives as Frozen Krill, Beefheart, Bloodworms, Mysis Shrimp.. The list goes on and on. However, I find a mixture of QUALITY Cichlid Pellets (the more variety in the mixture, the better) is the best daily use food. I usually feed frozen specialty foods on the weekends.
He should promote better coloration with a more nutritional diet, and good water quality will always help too!
Good Luck!