ΔE 8.7, close: similar, with a visible difference side by side. Purple Shadow is a little darker, more saturated, cooler than Volcano Brown.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Purple Shadow is a little darker, more saturated, cooler than Volcano Brown.
The same difference applies the other way round: Volcano Brown is a little lighter, more muted, 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 Volcano Brown on the colour wheel See Purple Shadow on the colour wheel
All matches: Volcano Brown equivalents · Purple Shadow equivalents