Costume

Description from the official Costume FAQ:


 * Costumes are items that are equipped into a character's costume slots to change their appearance. Costumes are decorative items only. They are worn over a character's existing armor without affecting any stats.

There are slots for costume headpieces and body pieces in the inventory window. Similar to guild capes and headgear, these slots have toggles you can set to show or hide your costume in combat areas or towns and outposts. Costumes are automatically hidden during PvP matches.

Unlike armor, those costumes that can be dyed are usually not dyed gray by default; the default colors are noted on the individual articles.

Full costumes
Full costumes consist of a headpiece and a body piece. They can be purchased through the Guild Wars In-Game Store or the NCsoft store. All of these pieces can be dyed.

To receive a purchased costume see the Costume Maker. These NPCs can be found in Kamadan, Lion's Arch, Shing Jea Monastery and the Great Temple of Balthazar.

Festival hats
Festival hats are costume headpieces handed out as a reward during seasonal special events. They can be "registered" at a festival hat maker by showing it to him, and he can then create that hat for all characters on your account.

Most festival hats cannot be dyed. Those that can be dyed are marked with a (*) in the table below.