ΔE 13.1, fair: the same colour family, but not a straight swap. Turquoise (Phthalo) is a little darker, warmer than Nocturne Green. They are different kinds of paint: Citadel Nocturne Green is an opaque base/layer paint and Golden Turquoise (Phthalo) 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 13). Turquoise (Phthalo) is a little darker, warmer than Nocturne Green. They are different kinds of paint.
The same difference applies the other way round: Nocturne Green is a little lighter, 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 Nocturne Green on the colour wheel See Turquoise (Phthalo) on the colour wheel
All matches: Nocturne Green equivalents · Turquoise (Phthalo) equivalents