Sand Grey vs Greatcoat Green

How close are they?

ΔE 6.0, close: similar, with a visible difference side by side. Greatcoat Green is cooler than Sand Grey.

Can I use Greatcoat Green instead of Sand Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Greatcoat Green is cooler than Sand Grey.

Can I use Sand Grey instead of Greatcoat Green?

The same difference applies the other way round: Sand Grey is 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.