ΔE 13.9, fair: the same colour family, but not a straight swap. Russian AF Blue is noticeably darker than Frost Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Russian AF Blue is noticeably darker than Frost Blue.
The same difference applies the other way round: Frost Blue is noticeably lighter.
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.
See Frost Blue on the colour wheel See Russian AF Blue on the colour wheel
All matches: Frost Blue equivalents · Russian AF Blue equivalents