I wonder if it’s from the red light inside the vehicle hangar causing the hull material to reflect it?
That's precisely what it is. The reason? All lights on ship seem to pass through game geometry, not only cargo/SRV bay lights, but also engine lights, proximity warning lights in cockpit (very noticeable in Kraits) and headlights. You can test the headlights easily--land next to an Ody settlement at night facing the building and turn on the ship lights--the building will be lit brightly inside through solid windowless walls. And not only ship lights do this, fires in burning settlements also ignore geometry.
Why do these lights do this? Who knows? Probably performance optimization (shadows are expensive), ship headlights also would otherwise be blocked by ship kits on some ships (again, Kraits are the prime example of some kit pieces going straight on the headlights).
Anyways, it's only noticeable in certain situations when you go looking for it. IMO, fires in burning settlement buildings lighting up the outside is the most blatant example of this behaviour; the ship lights are pretty benign in comparison (I only now noticed after being pointed out about that glitch in this thread here).