Bright Warm Grey vs Russian AF Grey N.4

How close are they?

ΔE 7.8, close: similar, with a visible difference side by side. Russian AF Grey N.4 is a little darker, more saturated than Bright Warm Grey.

Can I use Russian AF Grey N.4 instead of Bright Warm Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Russian AF Grey N.4 is a little darker, more saturated than Bright Warm Grey.

Can I use Bright Warm Grey instead of Russian AF Grey N.4?

The same difference applies the other way round: Bright Warm 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.