ΔE 10.2, fair: the same colour family, but not a straight swap. Russ. AF Light Blue is a little lighter, more saturated, cooler than Grey-Blue 1920s-1930s.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Russ. AF Light Blue is a little lighter, more saturated, cooler than Grey-Blue 1920s-1930s.
The same difference applies the other way round: Grey-Blue 1920s-1930s is a little darker, 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.
See Grey-Blue 1920s-1930s on the colour wheel See Russ. AF Light Blue on the colour wheel
All matches: Grey-Blue 1920s-1930s equivalents · Russ. AF Light Blue equivalents