ΔE 11.5, fair: the same colour family, but not a straight swap. Transparent Cold Green is noticeably darker, more muted than Aeldari Emerald. They are different kinds of paint: Citadel Aeldari Emerald is a one-coat contrast-style paint and Green Stuff World Transparent Cold 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 12). Transparent Cold Green is noticeably darker, more muted than Aeldari Emerald. They are different kinds of paint.
The same difference applies the other way round: Aeldari Emerald is noticeably lighter, more saturated.
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 Aeldari Emerald on the colour wheel See Transparent Cold Green on the colour wheel
All matches: Aeldari Emerald equivalents · Transparent Cold Green equivalents