ΔE 13.5, fair: the same colour family, but not a straight swap. Light Sea Blue is a little lighter, more muted, cooler than French Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Light Sea Blue is a little lighter, more muted, cooler than French Blue.
The same difference applies the other way round: French Blue is a little darker, more saturated, 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 French Blue on the colour wheel See Light Sea Blue on the colour wheel
All matches: French Blue equivalents · Light Sea Blue equivalents