ΔE 14.3, fair: the same colour family, but not a straight swap. Phthalo Green (Blue Shade) is noticeably lighter than Coelia Greenshade. They are different kinds of paint: Citadel Coelia Greenshade is a wash/shade and Golden Phthalo Green (Blue Shade) 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). Phthalo Green (Blue Shade) is noticeably lighter than Coelia Greenshade. They are different kinds of paint.
The same difference applies the other way round: Coelia Greenshade is noticeably darker.
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 Coelia Greenshade on the colour wheel See Phthalo Green (Blue Shade) on the colour wheel
All matches: Coelia Greenshade equivalents · Phthalo Green (Blue Shade) equivalents