ΔE 10.6, fair: the same colour family, but not a straight swap. Viridis Green is a little lighter, more saturated than Akhelian Green. They are different kinds of paint: Citadel Akhelian Green is a one-coat contrast-style paint and Green Stuff World Viridis Green is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Viridis Green is a little lighter, more saturated than Akhelian Green. They are different kinds of paint.
The same difference applies the other way round: Akhelian Green is a little 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.
See Akhelian Green on the colour wheel See Viridis Green on the colour wheel
All matches: Akhelian Green equivalents · Viridis Green equivalents