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