ΔE 14.1, fair: the same colour family, but not a straight swap. Ink Black Green is a little darker, more muted, warmer than Lupercal Green. They are different kinds of paint: Citadel Lupercal Green is an opaque base/layer paint and Vallejo Ink Black 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 14). Ink Black Green is a little darker, more muted, warmer than Lupercal Green. They are different kinds of paint.
The same difference applies the other way round: Lupercal Green is a little lighter, 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 Lupercal Green on the colour wheel See Ink Black Green on the colour wheel
All matches: Lupercal Green equivalents · Ink Black Green equivalents