ΔE 8.1, close: similar, with a visible difference side by side. Nihilakh Oxide is more muted, warmer than Green Blue. They are different kinds of paint: AMMO by Mig Green Blue is an opaque base/layer paint and Citadel Nihilakh Oxide is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Nihilakh Oxide is more muted, warmer than Green Blue. They are different kinds of paint.
The same difference applies the other way round: Green Blue is more saturated, cooler.
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 Green Blue on the colour wheel See Nihilakh Oxide on the colour wheel
All matches: Green Blue equivalents · Nihilakh Oxide equivalents