From color variation and fin shape, as well as the description of how they are with each other, I would say that you have a pair. They could just be showing territorial displays, making one a dominant and one a submissive. My boys get all flashy all the time with each other, even tho they have lived with each other all their lives. From my breeding experience with these guys, and they're all I breed, I have found that they can start breeding at around 5-6 in. It seems some start sooner than others. It really is dependent upon tank variables and the fish's attitudes. I've had fish who refuse to breed, even after they are well into adulthood. I'd say grow them out a little bit more, keep an eye on tank stats and if they truly are a pair they'll lay eggs randomly for you.