I think it's a "looks good in print" issue. For the same reason the Hulk is green and not gray. If blue hair was normal there would be blue haired ppl (although to be fair, Wonder woman and Barda often look blue!) because it looks striking and colorful. Especially older characters where they had just primary colors to work with and black was expensive and brown just looked blah... so they went with Red and Yellow... the two colors left.
More women have red because they have more hair. Their skin is already yellow... so if they have a lot of hair they just look like yellow blobs (when color shades are limited), so they go with red.
I really like Bachalo for some of the more over-the-top books, but this one being kinda darker the art should really be more subtle and precise. Things are confusing as is with powers changing and new characters appearing... last we need is crazy art.