ΔE 10.2, fair: the same colour family, but not a straight swap. Flat Brown is a little lighter, more saturated, cooler than Dark Umber.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Flat Brown is a little lighter, more saturated, cooler than Dark Umber.
The same difference applies the other way round: Dark Umber is a little darker, 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 Dark Umber on the colour wheel See Flat Brown on the colour wheel
All matches: Dark Umber equivalents · Flat Brown equivalents