ΔE 7.0, close: similar, with a visible difference side by side. Royal Blue is more muted than Pearl Blue. They are different kinds of paint: Tamiya Pearl Blue is a pearl paint and Vallejo Royal Blue is an opaque base/layer 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 7). Royal Blue is more muted than Pearl Blue. They are different kinds of paint.
The same difference applies the other way round: Pearl 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 Pearl Blue on the colour wheel See Royal Blue on the colour wheel
All matches: Pearl Blue equivalents · Royal Blue equivalents