ΔE 9.9, close: similar, with a visible difference side by side. Phthalo Blue (Green Shade) is a little lighter, more muted than Royal Blue. They are different kinds of paint: Army Painter Royal Blue is an opaque base/layer 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.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Phthalo Blue (Green Shade) is a little lighter, more muted than Royal Blue. They are different kinds of paint.
The same difference applies the other way round: Royal Blue is a little darker, 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 Royal Blue on the colour wheel See Phthalo Blue (Green Shade) on the colour wheel
All matches: Royal Blue equivalents · Phthalo Blue (Green Shade) equivalents