Bastion Grey vs Green Grey

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Green Grey is a little darker, more muted, cooler than Bastion Grey.

Can I use Green Grey instead of Bastion Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Green Grey is a little darker, more muted, cooler than Bastion Grey.

Can I use Bastion Grey instead of Green Grey?

The same difference applies the other way round: Bastion Grey 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.