Canopy Green vs Goblin Flesh

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Goblin Flesh is a little darker, cooler than Canopy Green.

Can I use Goblin Flesh instead of Canopy Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Goblin Flesh is a little darker, cooler than Canopy Green.

Can I use Canopy Green instead of Goblin Flesh?

The same difference applies the other way round: Canopy Green is a little lighter, 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.