Gremlin Green vs Sap Green

How close are they?

ΔE 8.4, close: similar, with a visible difference side by side. Sap Green is a little darker, cooler than Gremlin Green.

Can I use Sap Green instead of Gremlin Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sap Green is a little darker, cooler than Gremlin Green.

Can I use Gremlin Green instead of Sap Green?

The same difference applies the other way round: Gremlin 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.