ΔE 8.4, close: similar, with a visible difference side by side. Flat Earth is more saturated, warmer than Flat Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Flat Earth is more saturated, warmer than Flat Brown.
The same difference applies the other way round: Flat Brown is more muted, 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 Flat Brown on the colour wheel See Flat Earth on the colour wheel
All matches: Flat Brown equivalents · Flat Earth equivalents