Snow Shadow vs Russian AF Blue

How close are they?

ΔE 18.0, loose: different enough that you should pick on purpose. Russian AF Blue is a little lighter, much more saturated, cooler than Snow Shadow.

Can I use Russian AF Blue instead of Snow Shadow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Russian AF Blue is a little lighter, much more saturated, cooler than Snow Shadow.

Can I use Snow Shadow instead of Russian AF Blue?

The same difference applies the other way round: Snow Shadow is a little darker, much more muted, 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.