ΔE 13.1, fair: the same colour family, but not a straight swap. Leather Brown is noticeably lighter, warmer than NATO Black.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Leather Brown is noticeably lighter, warmer than NATO Black.
The same difference applies the other way round: NATO Black is noticeably 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 Leather Brown on the colour wheel
All matches: NATO Black equivalents · Leather Brown equivalents