The inhabitants of Mars maintain a near-universal form of fashion in the form of leather harnesses, elaborate ornamentation, and (possible) cultural nudity.
As the people of Mars are culturally militant, with duels and conscription as a way of life, the possession of a battle harness is seen as essential attire to any proud Barsoomian. A harness not just holds one's weapons, but also denotes rank and status. To be stripped of one's harness is seen as shameful and humiliating.
A harness is made of leather straps, fitted with pouches and weapon mounts, and usually decorated with elaborate ornamentation. The leather straps themselves can vary greatly in size, shape and material. Weapon mounting include simple looped cords and metal rings to attach sheaths, scabbards and holsters.
Not all harnesses are fashioned the same, as differing styles are needed for different roles. The harness of a foot solider would differ greatly from the harness of a cavalryman, just as the fancy harness of a merchant or diplomat would differ from the worn, utilitarian harness of a solider or laborer. In the military, one's harness would also denote one's rank and colors — the markings of one's tribe or city state.
While basic attire is lacking, Martians put a lot of effort in cosmetic decoration in the form of jewelry and bejeweled harnesses. There are no gender bias with regards to this. The decorations used to denote military rank, colors and service includes feathered headdress, chest-plates and other ornamentation.
Black Martians are noted for covering their harnesses with precious stones and metals, as to entirely obscure the leather.
It is the custom to give or exchange jewelry as a sign of truce or friendship.
A matter of contention with fans is the issue of nudity within the canon works of Edgar Rice Burroughs' Barsoom Series. While the books repeatedly describe the "nakedness" of characters, certain ambiguity in the wording makes it unclear the extent of how fully cover the characters are.
Over the years, the collective imagination of Burroughs' Mars was shaped by fantasy artists, noted for the scantly-clad "beefcake" and "cheesecake" costumes and poses. In most cases, women lack proper harnesses, while men lack jewelry. Modesty is maintained with G-strings or breechcloths, and the placement of ornamentation used to coverup bare breasts.
By and large, this is a matter of personal preference, as individual readers would imagine the characters in their own way, just as artists would draw the characters as they see fit.