Seeing how many times this topic was discussed, I decided to make a lenghty post, ultimately explaining that Arc-V mystery.

Q. Why no one notice that Yuya, Yuto, Yugo and Yuri, as well as Yuzu and Serena, are different people, despite them having different hair color and eye color?

A. They actually don’t have different hair and eye color.

Wait, what?..

Many people, who watch anime, don’t ever realise that, but characters in anime and manga don’t actually have those crazy colors for hair and eyes, we could see on screen. Those are just stylistic choice. Those colors mostly represent some parts of their personality.

This practise actually predates anime by centuries. In traditional japanese theatre Kabuki colourful make-up and wigs were used to show character’s personality and archetype. 

Q. This is kinda hard to believe..

A. Just try to remember when in anime series that takes place in Japan, any character even addressed someone’s hair color. It would be too easy to say something like “Help me to find blue-haired girl”. But it never addressed, except it part of a plot (like Onizuka hair being bleached etc…) That’s because characters themselves don’t see that different colors, it’s only we, viewers, could see them.

Q. But it doesn’t make any sense! If characters are drawn that way, that’s how they should see each other!

A. Are characters from South Park sees each other as super-deformed big-headed creatures with same face or rather as real people? Are characters from “Cats” musical see each other as humans in tight suits? That’s just style.

Sailor Moon live-action series is a good example. Before magical transformation, all girls have normal hair:

Q. So, what color of hair and eyes they actually have?

A. We don’t know it. Probably, considering how characters have Japanese names, they have dark hair and dark eyes. But not necessary.