Colored females?

[jred]

Question for fellow fish people, I have a small group of acei ngara growing out and I would like to keep 4-5 as the breeding group but I have only 1 fish that is a clear female to me (somewhat greyish blue with rounded anal fin). However today I noticed another bluer acei holding which I had thought was maybe a male. Do females sometimes color up like that? Or is it possible I that the grey fish is actually not a acei ngara? The cichlid forum doesn't have any official photos of them so I just want to make sure before I start selling the others off. Any opinions welcome, thanks!

[Regalblue]

Ps. acei is basically monomorphic.  Vent them to see which are the females.

[Ron]

IME, a male Ps. acei "Ngara" has more blue iridescence on the face. As the fish get older, I also think some of the white coloring stays sharper on the males. However, I agree with Regalblue that judging monomorphic species based on color along isn't always definite. I'd consider it an educated guess.