The Blue Key is a key item that appears in Wario: Master of Disguise.
The Blue Key is, as the name states, is a small blue key.
The Blue Key can be found in a room in Allergia Gardens that requires the use of Arty Wario's blocks. The Blue Key can open the door of the same color to access a new area of Allergia Gardens. It is also one of two colored keys that can be found in the level with the other two being the Yellow Key and the Red Key.