Goblin Green vs Rotten Green

How close are they?

ΔE 27.3, loose: different enough that you should pick on purpose. Rotten Green is a little lighter, more muted, warmer than Goblin Green.

Can I use Rotten Green instead of Goblin Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Rotten Green is a little lighter, more muted, warmer than Goblin Green.

Can I use Goblin Green instead of Rotten Green?

The same difference applies the other way round: Goblin Green is a little darker, more saturated, cooler.

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.