ΔE 8.8, close: similar, with a visible difference side by side. Fire Red is a little lighter, cooler than Mournfang Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Fire Red is a little lighter, cooler than Mournfang Brown.
The same difference applies the other way round: Mournfang Brown is a little darker, 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 Mournfang Brown on the colour wheel See Fire Red on the colour wheel
All matches: Mournfang Brown equivalents · Fire Red equivalents