ΔE 12.7, fair: the same colour family, but not a straight swap. Grey Blue is a little lighter, more saturated, warmer than Shadow Blue.
✓ Two Thin Coats comparison chart lists these two as equivalents.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Grey Blue is a little lighter, more saturated, warmer than Shadow Blue.
The same difference applies the other way round: Shadow Blue is a little darker, more muted, 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 Shadow Blue on the colour wheel See Grey Blue on the colour wheel
All matches: Shadow Blue equivalents · Grey Blue equivalents