Royal Cloak vs Spirit Blue

How close are they?

ΔE 8.3, close: similar, with a visible difference side by side. Spirit Blue is more muted, cooler than Royal Cloak.

Can I use Spirit Blue instead of Royal Cloak?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Spirit Blue is more muted, cooler than Royal Cloak.

Can I use Royal Cloak instead of Spirit Blue?

The same difference applies the other way round: Royal Cloak is more saturated, warmer.

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.