Sanguine Base vs Nocturnal Red

How close are they?

ΔE 9.2, close: similar, with a visible difference side by side. Nocturnal Red is more muted than Sanguine Base.

Can I use Nocturnal Red instead of Sanguine Base?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Nocturnal Red is more muted than Sanguine Base.

Can I use Sanguine Base instead of Nocturnal Red?

The same difference applies the other way round: Sanguine Base 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.