ΔE 10.3, fair: the same colour family, but not a straight swap. Viridian Grim is a little lighter, more saturated than Magnolia Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Viridian Grim is a little lighter, more saturated than Magnolia Brown.
The same difference applies the other way round: Magnolia Brown is a little darker, more muted.
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 Magnolia Brown on the colour wheel See Viridian Grim on the colour wheel
All matches: Magnolia Brown equivalents · Viridian Grim equivalents