ΔE 12.7, fair: the same colour family, but not a straight swap. Burnt Red is more saturated, cooler than Flat Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Burnt Red is more saturated, cooler than Flat Brown.
The same difference applies the other way round: Flat Brown is 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 Flat Brown on the colour wheel See Burnt Red on the colour wheel
All matches: Flat Brown equivalents · Burnt Red equivalents