As for sexing them...I'm not sure, but there are a lot of differences between these two. Not sure if that is because of the individuals or because of the sex. There colors are different (the male has bolder colors, the female has some black/grey color in the head), how they act are different (the male is more aggressive), and the heads/mouth are different (the male has a larger head/mouth).
If you plan to breed them, I would recommend a tank where they are the ONLY fish.
Two males will fight to the death, so you need a plan in place in case you end up with two makes. You could also end up with two females, who would likely adapt to each other, provided the tank size is not too small.
My male has been flashing for a while. About 4 months last fall, then he moved and stopped doing it until now. When he has been flashing it is when the two of them our housed about a foot apart from each other. I got a ton of video of BJ and the Misses yesterday that I will be posting in my Bluespot Heaven thread. Here's a teaser:
The Misses
BJ Flashing
BJ When He Is Not Flashing
Video BJ and the Misses (the Misses is in the upper right corner of the tank)