ΔE 25.8, loose: different enough that you should pick on purpose. Ogryn Camo is noticeably darker, much more muted than Grass Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Ogryn Camo is noticeably darker, much more muted than Grass Green.
The same difference applies the other way round: Grass Green is noticeably lighter, much more saturated.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Grass Green on the colour wheel See Ogryn Camo on the colour wheel
All matches: Grass Green equivalents · Ogryn Camo equivalents