ΔE 6.3, close: similar, with a visible difference side by side. N4 Neutral Gray is a little darker than Basilicanum Grey. They are different kinds of paint: Citadel Basilicanum Grey is a one-coat contrast-style paint and Golden N4 Neutral Gray 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 6). N4 Neutral Gray is a little darker than Basilicanum Grey. They are different kinds of paint.
The same difference applies the other way round: Basilicanum Grey is a little lighter.
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 Basilicanum Grey on the colour wheel See N4 Neutral Gray on the colour wheel
All matches: Basilicanum Grey equivalents · N4 Neutral Gray equivalents