ΔE 12.0, fair: the same colour family, but not a straight swap. Flat Red is a little darker, warmer than Terracota.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Flat Red is a little darker, warmer than Terracota.
The same difference applies the other way round: Terracota 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 Terracota on the colour wheel See Flat Red on the colour wheel
All matches: Terracota equivalents · Flat Red equivalents