ΔE 25.0, loose: different enough that you should pick on purpose. Imperial Yellow is noticeably lighter, much more saturated than Hardened Leather.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Imperial Yellow is noticeably lighter, much more saturated than Hardened Leather.
The same difference applies the other way round: Hardened Leather is noticeably darker, much 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 Imperial Yellow on the colour wheel
All matches: Hardened Leather equivalents · Imperial Yellow equivalents