Dark Angels Green vs Heretic Turquoise

How close are they?

ΔE 20.1, loose: different enough that you should pick on purpose. Heretic Turquoise is a little darker, more muted, cooler than Dark Angels Green.

Can I use Heretic Turquoise instead of Dark Angels Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Heretic Turquoise is a little darker, more muted, cooler than Dark Angels Green.

Can I use Dark Angels Green instead of Heretic Turquoise?

The same difference applies the other way round: Dark Angels Green is a little lighter, 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.