Faded Green vs Interior Grey Green

How close are they?

ΔE 7.8, close: similar, with a visible difference side by side. Interior Grey Green is a little darker, more muted than Faded Green.

Can I use Interior Grey Green instead of Faded Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Interior Grey Green is a little darker, more muted than Faded Green.

Can I use Faded Green instead of Interior Grey Green?

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

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.