>>54755300She'd have less plumage like the other anon said, bon her tail, and possibly also atop her head. The color of her feathers would be much more dull-- probably close to how its shiny looks, actually. Maybe that's what Game Freak was going for there.
I suspect that the drabber appearance would also affect their behavior. They'd likely be less flamboyant and more timid. And that mirrors real-life birds, too. The males are the flashy dancers.
That being said, I'm glad they didn't implement any sexual dimorphism with this Pokémon, because I like female Quaqua, and I wouldn't want her to be a downgraded version of the male one appearance-wise. Nobody wants another Unfezant situation.