ΔE 10.4, fair: the same colour family, but not a straight swap. Fog Grey is a little lighter, more muted than Rainfall Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Fog Grey is a little lighter, more muted than Rainfall Blue.
The same difference applies the other way round: Rainfall Blue is a little darker, more saturated.
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 Rainfall Blue on the colour wheel See Fog Grey on the colour wheel
All matches: Rainfall Blue equivalents · Fog Grey equivalents