ΔE 10.4, fair: the same colour family, but not a straight swap. Chestnut Brown is a little lighter, warmer than NATO Black.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Chestnut Brown is a little lighter, warmer than NATO Black.
The same difference applies the other way round: NATO Black is a little 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 NATO Black on the colour wheel See Chestnut Brown on the colour wheel
All matches: NATO Black equivalents · Chestnut Brown equivalents