ΔE 14.9, fair: the same colour family, but not a straight swap. Mortarion Grime is noticeably lighter, warmer than Grove Hollow Shade.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Mortarion Grime is noticeably lighter, warmer than Grove Hollow Shade.
The same difference applies the other way round: Grove Hollow Shade is noticeably darker, 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 Grove Hollow Shade on the colour wheel See Mortarion Grime on the colour wheel
All matches: Grove Hollow Shade equivalents · Mortarion Grime equivalents