ΔE 16.2, loose: different enough that you should pick on purpose. Cerulean Blue Hue is a little darker, much more saturated than Royal Robes. They are different kinds of paint: Army Painter Royal Robes is a one-coat contrast-style paint and Golden Cerulean Blue Hue is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Cerulean Blue Hue is a little darker, much more saturated than Royal Robes. They are different kinds of paint.
The same difference applies the other way round: Royal Robes is a little lighter, much more muted.
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 Robes on the colour wheel See Cerulean Blue Hue on the colour wheel
All matches: Royal Robes equivalents · Cerulean Blue Hue equivalents