Anime where the vast majority of the cast have natural hair colours (brown, black, blonde, ginger, etc.), but one of them was just born with brightly coloured hair (bonus points if there’s no explanation and nobody ever questions it).
TV, 2019, 12 eps Me:- Author:8
Momo - Pink
TV, 2022, 11 eps Me:- Author:8
Tsubasa/Tsuyoshi - Light blue
TV, 2019, 12 eps Me:- Author:8
Chika - Pink
TV, 2017, 13 eps Me:- Author:10
Marulk - Blue
Movie, 2020, 1 ep Me:- Author:9
Prushka - Green
TV, 2016, 10 eps Me:- Author:6
Aqua - Aqua
TV, 2021, 13 eps Me:- Author:8
Eileen - White fading to pink
TV, 2022, 12 eps Me:- Author:9
Barbie - Mint green
TV, 2022, 12 eps Me:- Author:9
Anya - Pink
TV, 2022, 13 eps Me:- Author:9
Becky - Dark purple
TV, 2011, 24 eps Me:- Author:9
Rumiho - Pink
Movie, 2013, 1 ep Me:- Author:9
Patema - Teal
Music, 2016, 1 ep Me:- Author:8
Rin - Pink
TV, 2006, 14 eps Me:- Author:7
Yuki - Violet
TV, 2019, 12 eps Me:- Author:9
Gilda - Green
TV, 2021, 11 eps Me:- Author:3
Mujika - Violet
ONA, 2022, 1 ep Me:- Author:3
Uta - Blue
TV, 2011, 26 eps Me:- Author:7
Yuno - Pink
TV, 2015, 12 eps Me:- Author:8
Yuki - Light Pink, Megumi - Bright pink
TV, 2000, 19 eps Me:- Author:8
Momoko - Violet
Movie, 2018, 3 eps Me:- Author:8
Shui - Pink
TV, 2002, 38 eps Me:- Author:8
Pique - Pink, Edel/Uzura - Mint green
TV, 2017, 12 eps Me:- Author:8
Yumemi - Pink
TV, 2019, 12 eps Me:- Author:8
Kirari and Ririka - White with hints of blue
ONA, 2022, 6 eps Me:- Author:8
Tsuzura - Dark blue
TV, 2013, 26 eps Me:- Author:6
Chisaki - Purple
TV, 2022, 13 eps Me:- Author:4
Majima - Green
TV, 2009, 15 eps Me:- Author:4
Hitagi - Purple
TV, 2006, 26 eps Me:- Author:-
Shion/Mion - Lime green
TV, 2013, 13 eps Me:- Author:6
Maki - Pinkish red
TV, 2016, 13 eps Me:- Author:-
Yoshiko - Dark teal
TV, 2020, 13 eps Me:- Author:-
Rina - Pink
TV, 2014, 12 eps Me:- Author:-
Kofuku - Pink
OVA, 1993, 6 eps Me:- Author:-
Josuke - purple, Rohan - green, - Trish, pink (Thanks to MeanMrMusician for the suggestion!)
TV, 2023, 11 eps Me:- Author:10
Ai - Purple, Akane - Blue, Kana - Pinkish red
TV, 2023, 12 eps Me:- Author:9
The Konohoshi sisters - Purple fading to blue, Yuu - Pastel pink
TV, 2009, 24 eps Me:- Author:5
Komoe - Pink
TV, 2002, 52 eps Me:- Author:9
Madoka - Purple
TV, 2023, 12 eps Me:- Author:8
Rafina - Light blue
TV, 2016, 13 eps Me:- Author:8
Papika - Orangish pink
TV, 2023, 24 eps Me:- Author:9
Maomao - Green / Jinshi - Purple
TV, 2019, 25 eps Me:- Author:8
Machi - Pale green
