ΔE 10.1, fair: the same colour family, but not a straight swap. Battlefield Brown is a little darker, more saturated than Dark Leather.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Battlefield Brown is a little darker, more saturated than Dark Leather.
The same difference applies the other way round: Dark Leather is a little lighter, more muted.
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 Dark Leather on the colour wheel See Battlefield Brown on the colour wheel
All matches: Dark Leather equivalents · Battlefield Brown equivalents