Warhammer 40000: Boltgun Locations of Keys for Grand Elevator

After exiting airlock after initial room, go trough the container and you will arrive at
This will be the starting point for all the keys. Circumvent the gap by walking around it on left or right side, then walk down the corridor and you will find the red key (where shotgun blasts are) and to the right of that you will have all the consoles for the keys.
Each key insert starts a purge sequence so be prepared to fight.

From the previously established starting point look left and slightly down.
You will see faint purple light, drop down and walk over there.
Follow the lights for few steps and you will find that new door has appeared.
It will only appear if you previously inserted the red key, same will be true for yellow door and purple key.
Just go trough this airlock, deal with the mobs and do some parkour. The key will be at the top of furthest tower to the left.

Its basically mirror of purple key.
From the starting point look right and slightly down, you dont really see any yellow indicators but just drop down and walk like you did with the purple key.
Go trough this airlock and you will arive in a small arena. Right across the room key will be shielded by a forcefield with a console disabling it to the left. Just disable it and get ready to slay some xenos slay some xenos.
Prepare yourself before inserting the key since this last purge will include a Great Unclean One