Why the eyes of some Nematobrycon lacortei are not red?

[Nicky]

I got a few Nematobrycon lacortei. About half of them have beautiful red-eyes but the other half of the population do not. Cannot be male/female right? I thought the male and female is distinguished by their dorsal fins?

[MrTree]

good question.

that's also why some reference describe that it's not the key difference when differentiating it from palmeri.

In my case, I couldn't even get any with reddish eye.

[loupgarou]

the ones with red eyes are tainted by evil!