The issue is that .png (no alpha) texture color is RGB 20,20,20
In game after exporting mod for test .dds texture color is RGB 16,20,16?

Edit: I just checked other gray .png texture used in my mod with RGB 3x18 color.
Compressed .dds texture color is RGB 3x16 - still gray not green.
Edit 2: I tried gray .png RGB 21,21,21 color
Compressed .dds color is RGB 24,20,24 (pink) ?
Edit 3: .png RGB 25,25,25
After export/compressed RGB 24,24,24 - OK
In game after exporting mod for test .dds texture color is RGB 16,20,16?
Edit: I just checked other gray .png texture used in my mod with RGB 3x18 color.
Compressed .dds texture color is RGB 3x16 - still gray not green.
Edit 2: I tried gray .png RGB 21,21,21 color
Compressed .dds color is RGB 24,20,24 (pink) ?
Edit 3: .png RGB 25,25,25
After export/compressed RGB 24,24,24 - OK