ΔE 8.5, close: similar, with a visible difference side by side. Phthalo Blue (Green Shade) is more muted than Soulstone Blue. They are different kinds of paint: Citadel Soulstone Blue is a technical paint or medium 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.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Phthalo Blue (Green Shade) is more muted than Soulstone Blue. They are different kinds of paint.
The same difference applies the other way round: Soulstone 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 Soulstone Blue on the colour wheel See Phthalo Blue (Green Shade) on the colour wheel
All matches: Soulstone Blue equivalents · Phthalo Blue (Green Shade) equivalents