ΔE 9.0, close: similar, with a visible difference side by side. Russ. AF Grey Blue is a little darker than Longbeard Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Russ. AF Grey Blue is a little darker than Longbeard Grey.
The same difference applies the other way round: Longbeard Grey is a little lighter.
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.
See Longbeard Grey on the colour wheel See Russ. AF Grey Blue on the colour wheel
All matches: Longbeard Grey equivalents · Russ. AF Grey Blue equivalents