ΔE 6.5, close: similar, with a visible difference side by side. Midnight Blue is a little lighter, more saturated than Nuln Oil. They are different kinds of paint: Citadel Nuln Oil is a wash/shade and Reaper Midnight 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 6). Midnight Blue is a little lighter, more saturated than Nuln Oil. They are different kinds of paint.
The same difference applies the other way round: Nuln Oil is a little darker, 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 Nuln Oil on the colour wheel See Midnight Blue on the colour wheel
All matches: Nuln Oil equivalents · Midnight Blue equivalents