[prodestrian]

When the production team dressed the basement, they built a replica of the coal bin door for the Containment Unit false wall. The whole assembly would've looked roughly something like this:

Or:

Definitely the first image (or something close to it), the end of the wall is clearly angled (not straight, and not 90 degrees unless the camera is playing tricks somehow with the brick direction):



It's possible their false wall joins onto the existing angled wall, the set designer may have replicated the other red door just in case they were going to film from that far back and the original red door would be visible, so they'd want the two to match. Who knows?

Not really much more visibility of the other side of the basement in the film though:


Edit: Given that the original walls are white but the walls which were visible are all tan/cream coloured, I wonder if that colour was added by the production in 84? So the set builders repainted the entire basement to match their fake walls, rather than painting their fake walls to match the original basement colour? If so, maybe they're the ones who repainted the original door red as well, so it would match the replica they built for the fake wall? In that case, what we're seeing in that more recent photo of the remaining door and wall might be the actual correct paint colours for both the walls (tan/cream) AND the ECU (red). Again, all speculation at this point.

[Kingpin]

Given that the original walls are white but the walls which were visible are all tan/cream coloured, I wonder if that colour was added by the production in 84? So the set builders repainted the entire basement to match their fake walls, rather than painting their fake walls to match the original basement colour? If so, maybe they're the ones who repainted the original door red as well, so it would match the replica they built for the fake wall?

Those are both reasonable assumptions.

It's unfortunate that due to the circumstances and technological constraints of 2010, we don't have the Pantone details... As the basement of Fire Station №23 has now received heavy modification for the refurbishment, those original paints have probably either been removed or covered over by now.