Permanent Green Light vs Goblin Green

How close are they?

ΔE 23.9, loose: different enough that you should pick on purpose. Goblin Green is a little lighter, warmer than Permanent Green Light.

Can I use Goblin Green instead of Permanent Green Light?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Goblin Green is a little lighter, warmer than Permanent Green Light.

Can I use Permanent Green Light instead of Goblin Green?

The same difference applies the other way round: Permanent Green Light is a little darker, 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.