ΔE 5.7, very close: most people won’t see a difference side by side. Phthalo Blue (Green Shade) is more muted than Celestium Blue. They are different kinds of paint: Citadel Celestium Blue is a one-coat contrast-style paint and Golden Phthalo Blue (Green Shade) is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Yes, for most jobs. Very close match (ΔE 6). Phthalo Blue (Green Shade) is more muted than Celestium Blue. They are different kinds of paint.
The same difference applies the other way round: Celestium Blue is 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 Celestium Blue on the colour wheel See Phthalo Blue (Green Shade) on the colour wheel
All matches: Celestium Blue equivalents · Phthalo Blue (Green Shade) equivalents