ΔE 12.0, fair: the same colour family, but not a straight swap. Middle Stone is more muted, warmer than Yellow Green FS-34259.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Middle Stone is more muted, warmer than Yellow Green FS-34259.
The same difference applies the other way round: Yellow Green FS-34259 is 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 Yellow Green FS-34259 on the colour wheel See Middle Stone on the colour wheel
All matches: Yellow Green FS-34259 equivalents · Middle Stone equivalents