ΔE 11.9, fair: the same colour family, but not a straight swap. Medieval Forest is a little darker, more saturated, cooler than Field Grey Highlight FS-34414.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Medieval Forest is a little darker, more saturated, cooler than Field Grey Highlight FS-34414.
The same difference applies the other way round: Field Grey Highlight FS-34414 is a little lighter, more muted, 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 Field Grey Highlight FS-34414 on the colour wheel See Medieval Forest on the colour wheel
All matches: Field Grey Highlight FS-34414 equivalents · Medieval Forest equivalents