Crusader Skin vs Shadow Flesh

How close are they?

ΔE 15.5, loose: different enough that you should pick on purpose. Shadow Flesh is noticeably darker, more saturated, cooler than Crusader Skin.

Can I use Shadow Flesh instead of Crusader Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Shadow Flesh is noticeably darker, more saturated, cooler than Crusader Skin.

Can I use Crusader Skin instead of Shadow Flesh?

The same difference applies the other way round: Crusader Skin is noticeably lighter, more muted, warmer.

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.