Shamrock Green vs Orc Skin

How close are they?

ΔE 38.7, loose: different enough that you should pick on purpose. Orc Skin is noticeably darker, much more muted than Shamrock Green.

Can I use Orc Skin instead of Shamrock Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 39). Orc Skin is noticeably darker, much more muted than Shamrock Green.

Can I use Shamrock Green instead of Orc Skin?

The same difference applies the other way round: Shamrock Green is noticeably lighter, 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.