ΔE 7.1, close: similar, with a visible difference side by side. Transparent Brown Iron Oxide is a little darker than Hardened Leather. They are different kinds of paint: Army Painter Hardened Leather is a one-coat contrast-style paint and Golden Transparent Brown Iron Oxide is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Transparent Brown Iron Oxide is a little darker than Hardened Leather. They are different kinds of paint.
The same difference applies the other way round: Hardened Leather is a little lighter.
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 Transparent Brown Iron Oxide on the colour wheel
All matches: Hardened Leather equivalents · Transparent Brown Iron Oxide equivalents