Grotesque Green vs Gray FS16440

How close are they?

ΔE 9.9, close: similar, with a visible difference side by side. Gray FS16440 is a little darker, more muted, cooler than Grotesque Green.

Can I use Gray FS16440 instead of Grotesque Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Gray FS16440 is a little darker, more muted, cooler than Grotesque Green.

Can I use Grotesque Green instead of Gray FS16440?

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