ΔE 14.7, fair: the same colour family, but not a straight swap. Transparent Turquoise is noticeably lighter, more saturated, warmer than Incubi Darkness. They are different kinds of paint: Citadel Incubi Darkness is an opaque base/layer paint and Green Stuff World Transparent Turquoise 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 15). Transparent Turquoise is noticeably lighter, more saturated, warmer than Incubi Darkness. They are different kinds of paint.
The same difference applies the other way round: Incubi Darkness is noticeably darker, more muted, 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 Incubi Darkness on the colour wheel See Transparent Turquoise on the colour wheel
All matches: Incubi Darkness equivalents · Transparent Turquoise equivalents