ΔE 16.1, loose: different enough that you should pick on purpose. USAF Light Blue is noticeably lighter, more saturated than Dark Eternal Night.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). USAF Light Blue is noticeably lighter, more saturated than Dark Eternal Night.
The same difference applies the other way round: Dark Eternal Night is noticeably darker, more muted.
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 Dark Eternal Night on the colour wheel See USAF Light Blue on the colour wheel
All matches: Dark Eternal Night equivalents · USAF Light Blue equivalents