ΔE 8.5, close: similar, with a visible difference side by side. Mud Brown is a little lighter, warmer than Black Rose Immortal.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Mud Brown is a little lighter, warmer than Black Rose Immortal.
The same difference applies the other way round: Black Rose Immortal is a little darker, 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 Black Rose Immortal on the colour wheel See Mud Brown on the colour wheel
All matches: Black Rose Immortal equivalents · Mud Brown equivalents