The blue box is supposed to show that the male has more bright blue specks on its sides, especially on the upper half compared to females.
And yes in most cases females will have shorter more rounded anal fins, this is not always the case.
I dont think they pair up as readily as convicts
Feed them a good pellet like Hikari Bio Gold or NLS, and supplement that with some high quality live foods, like little pieces of shrimp, krill, earth worms (Brineshrimp and Bloodworms for juvies)
Temp should be between 78-82 probably on the higher end for breeding.
I personally have never bred them