IJN/IJA Aotake vs Phalanx Blue

How close are they?

ΔE 18.8, loose: different enough that you should pick on purpose. Phalanx Blue is noticeably lighter, more saturated, cooler than IJN/IJA Aotake.

Can I use Phalanx Blue instead of IJN/IJA Aotake?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Phalanx Blue is noticeably lighter, more saturated, cooler than IJN/IJA Aotake.

Can I use IJN/IJA Aotake instead of Phalanx Blue?

The same difference applies the other way round: IJN/IJA Aotake is noticeably darker, 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.