For the longest time I've always wondered why Sailor Moon's hair is yellow while Sailor Mercury's hair is blue. Initially I thought it represented the planets they're associated with. However, after digging deeper into Japanese animation I found out hair color is frequently used as a mechanism to differentiate character type and personality.
Characters with black hair usually have a strong sense of justice.They can be friendly and angry at the same time. Despite, their mysterious nature they are loyal and would do anything for their friends.
Most often characters with white hair is either mysterious, ethereal, or old. If the character is a male, he usually have mix feelings and can be an anti-hero on a random good day. Female with white hair tend to be either magical or spiritual.
Characters with grey hair has a mix persona from white and black. They are independent and usually have hidden powers
This is a common color for the protagonist and often time they are seen as normal. However, you'll be surprise because characters with this hair color have interesting talents despite their boring appearance.
Blue hair colored characters are not the type to seek advice but give advice. You may notice they often play the roles of teachers or confidants. They also have hidden supernatural powers.
Just like the color, characters with red hair are hot blooded. Most of the time they are feisty and adventurous. However, some male characters with red hair are more calm and discipline.
Yellow hair characters have many sides. There are mainly different personalities but one thing that unite them is their positive vibe, stubbornness, high energy. You can call them the life of the party.
Personality: Naive, confident, and romantic
Characters with green hair have a unique energy. They're capable of healing and bring peace to destruction. Which is why the are often sided with the protagonist.
This hair color signifies romance and innocence. Characters with this hair are daydreamers and have great desire to bring positive vibe to others. They are also prone to mask their sadness.