List of Characters by Hair Colour

Black

 * Connor
 * Lenalee Lee
 * Valvatorez

Blonde

 * Kain Highwind
 * Lucy Stillman
 * Minako Aino
 * Ventus

Blue

 * Lucina
 * Manfred "Specter" Vaeris
 * Naoto Shirogane
 * Nina Lora

Brown

 * Desmond Miles
 * Flora
 * Isaac Acker
 * Kili
 * Newton Geiszler
 * Tanis

Green

 * Rydia
 * Terra Branford

Multicoloured

 * Celia Espellomente (green with pink highlight, mostly green though)
 * Fatima (purple at roots, gradually turns blue at tips)
 * Shadow the Hedgehog (black, red, white)

Pink

 * Lightning Farron
 * Pinkie Pie
 * Serah Villiers Farron

Purple

 * Sophie Lhant

Red

 * Adell

White

 * Fran
 * Hope Estheim
 * Konayuki Itezora
 * Lioriley
 * Mjrn

Never takes off their headgear so who even knows

 * Altaïr Ibn-La'Ahad