ΔE 9.5, close: similar, with a visible difference side by side. Night Lords Blue is a little darker, more muted, warmer than Regal Blue.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Night Lords Blue is a little darker, more muted, warmer than Regal Blue.
The same difference applies the other way round: Regal Blue is a little lighter, more saturated, cooler.
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 Regal Blue on the colour wheel See Night Lords Blue on the colour wheel
All matches: Regal Blue equivalents · Night Lords Blue equivalents