ΔE 5.7, very close: most people won’t see a difference side by side. Chestnut Brown is a little darker, cooler than Flat Brown.
Yes, for most jobs. Very close match (ΔE 6). Chestnut Brown is a little darker, cooler than Flat Brown.
The same difference applies the other way round: Flat Brown is a little lighter, 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 Chestnut Brown on the colour wheel
All matches: Flat Brown equivalents · Chestnut Brown equivalents