You guys have it all wrong, it's not the food that they lost their colors. I feed mine NLS all the time.
I have a nice set of 6 cobue peacocks at 5". All fully color and beautiful. Have 3 ahlis at 5" and fully blue.
I bought several nice fully colored 4" peacocks from other local hobbyist (red shoulder, blue regal, ngara) ..they all lost thier colors due to the dominant peacocks and changed back to brown so they won't get picked on.
Only way to get their colors back, take these smaller males out of the tank into a different tank..they'll gain thier colors back, as long there are no bigger dominant male peacocks sharing that tank.
I've learned that the hard way.. my 4 inch males are regaining the colors and I'm letting them grow bigger until they reach full stage at 5" to put them back into the main tank.
IF you add a 5 incher male into a tank with other 5 incher male peacocks, chances the new male will retian its color..I've tried that experiment several months ago and it seems to work. everytime you pull the dominant male out of the tank, the next size male will take over and bloom its colors out.