ΔE 17.4, loose: different enough that you should pick on purpose. Alpha Blue is noticeably lighter, warmer than Power Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Alpha Blue is noticeably lighter, warmer than Power Blue.
The same difference applies the other way round: Power Blue is noticeably 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 Power Blue on the colour wheel See Alpha Blue on the colour wheel
All matches: Power Blue equivalents · Alpha Blue equivalents