ΔE 8.6, close: similar, with a visible difference side by side. Fire Red is a little lighter, more saturated, warmer than Red Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Fire Red is a little lighter, more saturated, warmer than Red Brown.
The same difference applies the other way round: Red Brown is a little darker, 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 Red Brown on the colour wheel See Fire Red on the colour wheel
All matches: Red Brown equivalents · Fire Red equivalents