They are quite easy to sex just looking at them in the tank, usually no need to vent.
As Canamonster mentioned, the one broadside view in you pic is obviously female.
Why not post side views of each?
Generally.....
The dark area in the dorsal is a female trait.
Here are two females.
Both have dark areas in the dorsal both torpedo shaped profiles,
Another shot of a female, somewhat less dark, but note the dorsal color.
Now compare to a male, (pushing around a female), no dark area in the dorsal, also note the extra iridescent spots in the dorsal
Note the shape of a male profile.
