ΔE 9.5, close: similar, with a visible difference side by side. Tainted Garden is a little lighter, cooler than Russian Dark Brown 6K.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Tainted Garden is a little lighter, cooler than Russian Dark Brown 6K.
The same difference applies the other way round: Russian Dark Brown 6K 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 Russian Dark Brown 6K on the colour wheel See Tainted Garden on the colour wheel
All matches: Russian Dark Brown 6K equivalents · Tainted Garden equivalents