ΔE 23.5, loose: different enough that you should pick on purpose. Heretic Turquoise is noticeably darker, much more muted, cooler than Akhelian Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Heretic Turquoise is noticeably darker, much more muted, cooler than Akhelian Green.
The same difference applies the other way round: Akhelian Green is noticeably lighter, much more saturated, 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.
See Akhelian Green on the colour wheel See Heretic Turquoise on the colour wheel
All matches: Akhelian Green equivalents · Heretic Turquoise equivalents