Longbeard Grey vs Gray FS26440

How close are they?

ΔE 7.3, close: similar, with a visible difference side by side. Gray FS26440 is a little darker, more saturated than Longbeard Grey.

Can I use Gray FS26440 instead of Longbeard Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Gray FS26440 is a little darker, more saturated than Longbeard Grey.

Can I use Longbeard Grey instead of Gray FS26440?

The same difference applies the other way round: Longbeard Grey is a little lighter, more muted.

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.