Fowler diesel 'Peldon' at Amberley museum: like many other dark green railway subjects, bringing outthe detail lightens the colour.

First, the camera's own jpeg, resized to 900 pixels high.
Camera jpeg
Second, from the raw photo at 0EV : experience shows dark greens turn paler in this proces.
0EV raw
Third, from the raw photo at -1EV : a bit dark, but let's see what happens.
-1EV for better starting point
Fourth, add +2EV to "correct" for any shadow detail, so actually +1EV.
+1EV for shadow detail
Fifth, subtract 2EV from "correct" for any highlight detail, so actually -3EV.
-3EV for highlights
At last, use the "Three Exposures" filter.
Three Exposures
Seventh, G'MIC Local contrast enhancement filter.
Local contrast enhancement
Eighth, the Advanced Tone mapping filter.
Tone mapping
Ninth, use the curves tool for a bit more contrast, a bit overdone.
Curve for contrast
Finally, sharpen with the Unsharp Mask.
Unsharp Mask