ΔE 11.6, fair: the same colour family, but not a straight swap. Caspian Blue is a little lighter, more muted than Abyssal Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Caspian Blue is a little lighter, more muted than Abyssal Blue.
The same difference applies the other way round: Abyssal 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 Abyssal Blue on the colour wheel See Caspian Blue on the colour wheel
All matches: Abyssal Blue equivalents · Caspian Blue equivalents