Hardened Leather vs Phoenix Feather

How close are they?

ΔE 21.3, loose: different enough that you should pick on purpose. Phoenix Feather is noticeably lighter, much more muted than Hardened Leather.

Can I use Phoenix Feather instead of Hardened Leather?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Phoenix Feather is noticeably lighter, much more muted than Hardened Leather.

Can I use Hardened Leather instead of Phoenix Feather?

The same difference applies the other way round: Hardened Leather is noticeably darker, much 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.