ΔE 9.6, close: similar, with a visible difference side by side. Parasite Brown is a little lighter, more saturated than Hardened Leather. They are different kinds of paint: Army Painter Hardened Leather is a one-coat contrast-style paint and Vallejo Parasite Brown is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
✓ Herrick Games paint comparison chart lists these two as equivalents.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Parasite Brown is a little lighter, more saturated than Hardened Leather. They are different kinds of paint.
The same difference applies the other way round: Hardened Leather is a little darker, more muted.
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 Hardened Leather on the colour wheel See Parasite Brown on the colour wheel
All matches: Hardened Leather equivalents · Parasite Brown equivalents