ΔE 10.5, fair: the same colour family, but not a straight swap. Middle Stone is a little lighter, cooler than Brown Green.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Middle Stone is a little lighter, cooler than Brown Green.
The same difference applies the other way round: Brown Green is a little darker, 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 Brown Green on the colour wheel See Middle Stone on the colour wheel
All matches: Brown Green equivalents · Middle Stone equivalents