Absolution Green vs Akhelian Green

How close are they?

ΔE 24.1, loose: different enough that you should pick on purpose. Akhelian Green is noticeably lighter, cooler than Absolution Green.

Can I use Akhelian Green instead of Absolution Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Akhelian Green is noticeably lighter, cooler than Absolution Green.

Can I use Absolution Green instead of Akhelian Green?

The same difference applies the other way round: Absolution Green is noticeably darker, 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.