Sounds like there may be a panel_L.bmp in teh texture folder with a light gray texture used as self illumination.
Go to the panel folder and find the name of the bmp used as (for example vc01.bmp) attached to vcockpit01 section.
Find that named bmp with an _L in the texture folder.
For example:
[Vcockpit01]
file=vc01.bmp
Background_color=0,0,0
size_mm=1024,1024
visible=0
pixel_size=1024,1024
texture=$vc03
Then in the texture folder find:
vc01_L.bmp
That is your "light map" for that vcockpit section.
That texture is used at night when lights are turned on to act as additive lighting to the panel surface.
Open that texture. If it is solid gray, then that will brighten up all your panel surface and gauges for that section. You can make it darker, say around 50,50,50 or less, and it should be more subtle. FS adds the light values of 50,50,50 to the existing panel at night with lights out to brighten the panel.
If the bmp is a copy of the daytime panel section with gauge holes colored in with light grays, you can darken the panel surface (20,20,20) and simply leave a nice medium to dark gray (50,50,50 or more) in the gauge holes for backlighting the gauges.
Hope this helps.
EDIT: BTW, if you find an upside down panel in that texture, that is correct. You can flip it to work on it if your wish, just flip it back when done.