I've had a trio of P. polit (a male and two females) for about 6 months or so now. The male has never really coloured up properly, which was really disappointing. So this weekend I bought another mature coloured male, with hopes that a little competition would at least keep one of them coloured (didn't matter which). Seems to have worked like a charm. The original male seems to have asserted dominance over the newbie, and appears to be willing to hold his colour now. I got a few shots of him tonight.
Displaying to one of the females:
Displaying to one of the females: