ΔE 24.8, loose: different enough that you should pick on purpose. Mortarion Grime is noticeably lighter, more muted, cooler than Strong Tone.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Mortarion Grime is noticeably lighter, more muted, cooler than Strong Tone.
The same difference applies the other way round: Strong Tone is noticeably darker, more saturated, warmer.
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 Strong Tone on the colour wheel See Mortarion Grime on the colour wheel
All matches: Strong Tone equivalents · Mortarion Grime equivalents