Goblin mail is the armour worn by goblins that they may sometimes drop when killed. Players can also sometimes find some when searching some of the crates in the Goblin Village. Players cannot normally wear it, although three sets of it are required for the Goblin Diplomacyquest.
During the Land of the Goblins quest the player can turn into a goblin using a transmogrification potion in the Goblin Cave and must dye some goblin armour, each of the colours listed below in order to access restricted tribal areas. The only exceptions are red, green and pink, they have no tribes in those corresponding colours (The red-wearing Thorobshuun and green-wearing Garagorshuun tribes can be found in Goblin Village and it is unknown if there is or ever was a pink-wearing goblin tribe).
Most colours can be made by using the appropriate dye, but white and black require special items.
The current store price for set of one goblin mail is 6 to 16 coins. In RuneScape Classic the price was an astounding 50 coins, three times more than the price before goblin mail demand increased. New players were delighted to find goblin mail for the somewhat high store value. The Wise Old Man in Draynor will pay 60 coins for coloured mail, an easy (if somewhat tedious and quite slow) method to make money, as dye only costs 5 coins (and some freely-available ingredients) and goblins aren't difficult to kill even at low levels.
The original un-dyed goblin mail is also known as "brown goblin mail" as stated in Goblin Diplomacy.
There was a glitch where it is possible to wear goblin mail as a human. When this occurs, the player's arms will be detached and their torso will be missing. The glitch was done by wearing the goblin mail in the goblin temple during the Land of the Goblin quest and then saving to the equipment preset. This glitch is no longer possible because of an update making it so that you can only save equipment presets while banking. Attempting to save an equipment preset without a bank will give a message saying that you need the bank interface opened.