WWI French Green 2 vs Black Grey

How close are they?

ΔE 6.8, close: similar, with a visible difference side by side. Black Grey is more muted than WWI French Green 2.

Can I use Black Grey instead of WWI French Green 2?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Black Grey is more muted than WWI French Green 2.

Can I use WWI French Green 2 instead of Black Grey?

The same difference applies the other way round: WWI French Green 2 is 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.