ΔE 21.2, loose: different enough that you should pick on purpose. Turquoise is noticeably lighter, much more saturated, warmer than Ashen Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Turquoise is noticeably lighter, much more saturated, warmer than Ashen Blue.
The same difference applies the other way round: Ashen Blue is noticeably darker, much 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 Ashen Blue on the colour wheel See Turquoise on the colour wheel
All matches: Ashen Blue equivalents · Turquoise equivalents