I had a group of 6, your parrot will color up once he's all settled in. Looks like those are stress colors to me. They become very dark. It could also be the lighting on your tank making the fish become dark. Substrate and lighting has a lot to do with coloration of fish. I feel they're a species that is better kept in groups of their own kind. As for sex it's very hard to tell these fish apart unless they pair up on their own. Both males and females look very similar and fin rounding can't be used here to determine sex as both genders seem to have pointy fins