Sexing fry by color, or size is not very reliable.

I also don't understand why you are using a flashlight to try to see the sexual fins.

The male fry could be too young to have developed their gonapodiums.

However, the females should be showing their "gravid spots" now, or soon.  If you know what a gravid spot is, then follow me through this method that I use to separate fry.

Please understand that if this sounds simplistic, do not take it personally, I am not trying to be condescending in any way, only specific.

You did not mention the gravid spot in your write up so I don't want to assume anything.

A gravid spot is an area on females that is dark in color, located in the abdomen near the anal fins, and appears very early in life.

Since the gonopodium in males takes longer to develop, I use the gravid spot in the females to begin separating my fry.

I don't remember in what type of tank you had placed your fry, so my description will be general as well, for lurkers too.

What I do is use a white background behind the tank, a white wall or even a piece of white paper.

Then I set up a bright light near the tank to illuminate the bodies of the fry.

You can use a flashlight, but I find it easier if I'm not holding anything other than the fry net.

I also suggest using a fry net.  
They are of a finer mesh, which decreases the chances of injury, and are also usually white, which also helps.

Then I look for the dark spots on the abdomens of the females, and net them, removing them from the males.

I realize now, that I have often stated that, "I separate my males from my females as soon as I can determine their sex".  

What I actually do is separate my FEMALES FROM MY MALES.

In retrospect, I realize this isn't really the same thing, so thanks for pointing it out to me by your posting.

Rememer as well, that if the fry are too young to have a gonopodium, then they are too young to procreate as well.  

That may sound really obvious, but it may help someone who is going crazy wanting to sex their fry to prevent future litters.

I hope this helps you to determine the sex of, and separate your fry.

I also really, really, really, hope that when I do some various searches, this will show up.

Good luck, and keep us posted.