Noble Skin vs Dark Green

How close are they?

ΔE 23.7, loose: different enough that you should pick on purpose. Dark Green is much more saturated, cooler than Noble Skin.

Can I use Dark Green instead of Noble Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Dark Green is much more saturated, cooler than Noble Skin.

Can I use Noble Skin instead of Dark Green?

The same difference applies the other way round: Noble Skin is much 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.