The annoying thing is that their hair was part of their character. Bubbles' hair is puffy and cutesy 'cause she's the girly one, Buttercup is boyish and rash so her hair is short, and Blossom's hair represents a flowing cape because she's heroic and the team leader. The Powerpuff Girls' designs are deceptively simple looking, but every part of their design is to illustrate who they are.
Even Bliss in the reboot has some symbolism in her hair; her bangs are supposed to resemble the bangs of all three girls put together, in a meta sense because she was made after the original trio and takes inspiration from them. I don't like the reboot but even that crap had something half-decent.
If they really wanted to make a black puff, they'd have to at least give it more forethought than random lumps of hair. Blossom could have straight hair, Bubbles has puffs, and Buttercup could have braids that stick off the side of her head like her original hair did, at least then there'd be an effort to stick to original ideas.