Spectrum Blue vs Rus. AF Grey Prot. Coat

How close are they?

ΔE 9.3, close: similar, with a visible difference side by side. Rus. AF Grey Prot. Coat is a little lighter, more saturated than Spectrum Blue.

Can I use Rus. AF Grey Prot. Coat instead of Spectrum Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Rus. AF Grey Prot. Coat is a little lighter, more saturated than Spectrum Blue.

Can I use Spectrum Blue instead of Rus. AF Grey Prot. Coat?

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