ΔE 16.4, loose: different enough that you should pick on purpose. Primary Blue is noticeably lighter, more saturated, warmer than Phalanx Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Primary Blue is noticeably lighter, more saturated, warmer than Phalanx Blue.
The same difference applies the other way round: Phalanx Blue is noticeably 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 Phalanx Blue on the colour wheel See Primary Blue on the colour wheel
All matches: Phalanx Blue equivalents · Primary Blue equivalents