ΔE 24.5, loose: different enough that you should pick on purpose. Mortarion Grime is noticeably lighter, much more muted, warmer than Green Tone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Mortarion Grime is noticeably lighter, much more muted, warmer than Green Tone.
The same difference applies the other way round: Green Tone is noticeably darker, much more saturated, cooler.
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 Green Tone on the colour wheel See Mortarion Grime on the colour wheel
All matches: Green Tone equivalents · Mortarion Grime equivalents