ΔE 16.2, loose: different enough that you should pick on purpose. Light Sea Blue is much more saturated, cooler than RAF Azure Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Light Sea Blue is much more saturated, cooler than RAF Azure Blue.
The same difference applies the other way round: RAF Azure Blue is much 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 RAF Azure Blue on the colour wheel See Light Sea Blue on the colour wheel
All matches: RAF Azure Blue equivalents · Light Sea Blue equivalents