ΔE 11.6, fair: the same colour family, but not a straight swap. Nocturne Green is more muted, cooler than Fluorescent Blue. They are different kinds of paint: AK Interactive Fluorescent Blue is a fluorescent or effect paint and Citadel Nocturne Green is an opaque base/layer 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 12). Nocturne Green is more muted, cooler than Fluorescent Blue. They are different kinds of paint.
The same difference applies the other way round: Fluorescent Blue is 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.
See Fluorescent Blue on the colour wheel See Nocturne Green on the colour wheel
All matches: Fluorescent Blue equivalents · Nocturne Green equivalents