ΔE 11.1, fair: the same colour family, but not a straight swap. Sky Blue is a little lighter, more muted, warmer than Interior Blue Soviet.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Sky Blue is a little lighter, more muted, warmer than Interior Blue Soviet.
The same difference applies the other way round: Interior Blue Soviet is a little darker, more saturated, cooler.
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 Interior Blue Soviet on the colour wheel See Sky Blue on the colour wheel
All matches: Interior Blue Soviet equivalents · Sky Blue equivalents