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