Nature Green vs Sick Green

How close are they?

ΔE 22.8, loose: different enough that you should pick on purpose. Sick Green is a little darker, much more muted, cooler than Nature Green.

Can I use Sick Green instead of Nature Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sick Green is a little darker, much more muted, cooler than Nature Green.

Can I use Nature Green instead of Sick Green?

The same difference applies the other way round: Nature Green is a little lighter, much more saturated, 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.