Action Heroine Cheer Fruits is one of those shows where the names of the lead characters contain names of colors, and those names match up to some color theme that the character has (in this case, it's the characters' hair colors).
Except... it only does it for some of the main characters, which is weird.
Characters that are "color-coded"
Akagi An (aka = 赤 = "red"); Midorikawa Mana (midori = 緑 = "green"); Aoyama Genki and her sister Aoyama Yuuki (ao = 青 = "blue"); Momoi Hatsuri (momo = 桃 = "pink" / "peach")
Characters that aren't "color-coded"
Shirogane Misaki (shiro, written differently = 白 = "white"); Kuroki Roko (kuro = 黒 = "black"); Kise Mikan (ki = 黄 = "yellow"); Shimura Kanon (shi = 紫 = "purple")
I guess there might not be a deeper answer to my question than "because that's how they decided to write it"; I just can't help wondering if I'm missing out on some next-level punnery or something. (Seeing as we already have nonrealistic green- and blue-haired characters, as well as yellow- and black-haired ones who aren't the characters with those colors in their names, it wouldn't be much of a stretch to add purple- and white-haired characters into the mix.)