Here... it's just easier to SHOW you than to try to explain. . . these are two of my little brats:
The shot above is a male, see how thin and angled his vent is? It's really hardly there - my other male looks just the same.
The shot below is a female, see how thick her vent is, and the way it angles downward a bit more? It's very obviously there. . . and shaped as such so that she can release eggs. All of my girls look like this one.
You can't really tell with these guys by coloration, or elongated top-fins, or the filaments on their tails, etc, because these traits have been selectively bred into both genders at this point. . .
Hope that helps you to get a handle on the genders of your little ones! Be cautious when introducing a new Livie to the group - they can get snarky!!!
And I don't even SEE the background you guys are talking about! Maybe I have to go through the videos again, I was having too much fun looking at the beautiful fish and plants!!!