Red Leather vs Nocturnal Red

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Nocturnal Red is a little darker, more saturated than Red Leather.

Can I use Nocturnal Red instead of Red Leather?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Nocturnal Red is a little darker, more saturated than Red Leather.

Can I use Red Leather instead of Nocturnal Red?

The same difference applies the other way round: Red Leather is a little lighter, 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.