Hardened Leather vs Radiant Orange

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Radiant Orange is noticeably darker, more muted than Hardened Leather.

Can I use Radiant Orange instead of Hardened Leather?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Radiant Orange is noticeably darker, more muted than Hardened Leather.

Can I use Hardened Leather instead of Radiant Orange?

The same difference applies the other way round: Hardened Leather is noticeably lighter, more saturated.

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.