usually brighter throat, pointy fins, and a more sloped head means male. I'd say the one in the back is male, but the color of the one up front makes me question if its not female.
There is no way of telling from the photo what sex they are.
If the two sexes where side by side the male would eventually outgrow the female.
Fin extensions can be prominent on both sexes and some females are just as bright as males.
I normally keep them in groups.In a group situation I find you can sex them by their behaviour.
Sorry but sexing these two would just be guessing.
When in courting and spawning mode, the females sometimes get a dark colored blotch in the dorsal, but not always. And I agree with the others, noway to tell at thi point.