The color is actually Dull Dark Green..it was introduced in 1942 as a matte replacement for semi-gloss Bronze Green (to cut down reflections) Both colors are very similar. They don't actual FS numbers, as that color system didn't exist yet..but 34092 seems to be a close match. On B-17s, DDG is correct for the nose, cockpit, and radio room. If you want to get picky, the original specs call for only the exposed metal parts to be painted..most of the interior was covered with padding that was dyed either dark green or OD. It was usually ripped out in service, exposing the bare metal structure. By the time the G's came along, most of the padding and most of the interior paint had been dispensed with to speed up production. On a wartime Fort, the bomb bay was usually Neutral Gray on camouflaged aircraft, and unpainted on bare metal birds. All B-17s were pretty much unpainted inside aft of the radio room.
Of course, most restorations have been painted inside for maintenance and preservation..when they were originally built they were only expected to be around for a few months, so long term corrosion protection wasn't really much of a concern. Yankee Lady has similar interior colors to SSSB, with DDG in the cockpit and nose, but Interior Green everywhere else inside.
For modeling purposes, nobody makes specific Dull Dark Green, but Testors Model Master "Euro 1 Dark Green" FS34092 is a decent substitute. I prefer Humbrol for brushing, and for DDG I've got a few carefully hoarded tins of HB-1 Dark Green from the old "Authentic Colors" line. The stuff is at least 30 years old, but still as good as it was when it was made.
Here are some original examples of Dull Dark Green, courtesy of Albert Stix..who was kind enough to send me a few bits from his massive stash of NOS turret parts.

Here's a snapshot of the cockpit of the Memphis Belle..while a lot of it was sprayed Interior Green during her refurbishment in the 1980s, you can still see the original Bronze Green or Dull Dark Green below the throttle console and at the base of the control columns..

And here's the unrestored cockpit of The Swoose. (the seats and panel have been removed.) You can see the exposed parts are either Bronze Green or DDG. The padding was originally dark green or OD, but has faded to a red-brown.

DDG was also used in the cockpit and nose of B-24s. Some years ago the nose compartment of the Strawberry Bitch was painted Interior Green throughout, but here are a few photos taken of her in her original state (courtesy of Karl Hauffe.)



SN