Can anyone explain why this aran

Can anyone explain why this aran have different look?

Because he's not you.
I'd assume the outfits are client sided.

From a story perspective, he could be another warrior, while you are the HERO.

When you look at other characters in that area, they appear to be different, but on their screens they're the same.

Because you only see yourself as the Aran hero in your screen. The rest are like... apprentices. The other guys is seeing the same screen as you, that means: he's the hero and you the apprentice.

EDIT: Double f'ucking ninja'd. What's wrong with you dudes.