As mentioned, you'll first need to remove all of the Tunnel Crates to even access the door. Then, you need to open several doors before accessing the Blue Door. Here's how to open the first six doors ...
During Du or Die, you're tasked to steal uranium from Fort Quito. Inside Fort Quito's basement, you'll find a locked door with a crocodile skin weapon chest inside. Here's how to find the Fort Quito ...