AII Light Blue vs Russ. AF Grey N.8

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Russ. AF Grey N.8 is a little lighter, cooler than AII Light Blue.

Can I use Russ. AF Grey N.8 instead of AII Light Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Russ. AF Grey N.8 is a little lighter, cooler than AII Light Blue.

Can I use AII Light Blue instead of Russ. AF Grey N.8?

The same difference applies the other way round: AII Light Blue is a little darker, 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.