A White Door is a type of Door from Metroid Prime, as well as Metroid: Zero Mission and Metroid Fusion. They are the third type of door encountered during Prime, requiring the use of the Ice Beam to open them. In Metroid: Zero Mission and Metroid Fusion, however, the White Door acts as an all-access door, requiring no special weaponry to open.
Metroid: Zero Mission
In Metroid Prime, White Doors are the third type of door that Samus encounters, first encountering them on her visit to the Furnace. In Prime, White Doors require the Ice Beam to open. Unlike their more permissive counterparts the Blue Doors, White Doors are not commonly paired with Missile Door Locks.