Blue dye is a dye made by Aggie the witch or Ali the dyer from 2 woad leaves at a cost of 5 coins (for a total of 25 coins, including the woad leaves cost). It can also be purchased from Oronwen, who owns the Lletya Seamstress.
Woad leaves can be purchased at Falador's park from Wyson the gardener or grown using the Farming skill.
It is used to turn capes and wizard hats blue in colour. Players can combine it with red dye to make purple dye or with yellow dye to make green dye. Players can also make black wizard hats blue by using the dye on them.
It is also used in some quests. For example, it is used to dye goblin mail in the Goblin Diplomacy and Land of the Goblins quests, and it also can also be used on the Ghosts Ahoy quest to paint a toy boat.
This item can be disassembled with the Invention