Unforgiven Green vs Blackroot Grey

How close are they?

ΔE 9.4, close: similar, with a visible difference side by side. Blackroot Grey is a little lighter, more muted than Unforgiven Green.

Can I use Blackroot Grey instead of Unforgiven Green?

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

Can I use Unforgiven Green instead of Blackroot Grey?

The same difference applies the other way round: Unforgiven Green is a little darker, 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.