Cold Green vs Aqua Alchemy

How close are they?

ΔE 16.1, loose: different enough that you should pick on purpose. Aqua Alchemy is noticeably lighter, more saturated than Cold Green.

Can I use Aqua Alchemy instead of Cold Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Aqua Alchemy is noticeably lighter, more saturated than Cold Green.

Can I use Cold Green instead of Aqua Alchemy?

The same difference applies the other way round: Cold Green 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.