Endler male color development

[SWilson]

Does anyone know if endler males will develop brighter/better coloration if they are kept with females vs separated out?  Or is their color genetically predisposed? I'm thinking about pulling my males for population control and to select which ones I want to breed in the future, but also wanted to try to give them to my lfs to also keep down the numbers (it's only a 16 gal tank).  They're already not too psyched about them because they say endlers don't sell very well around here due to being less colorful.     

[Wingman12r]

It could go either way. I've had some less colorful males I pulled from the breeding tank and added as dither to another tank that have colored up wonderfully. 

There could also be some dominance/ pecking order reasons why some don't show good color.