Black Rubber vs Night Blue

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Night Blue is a little lighter, more saturated than Black Rubber.

Can I use Night Blue instead of Black Rubber?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Night Blue is a little lighter, more saturated than Black Rubber.

Can I use Black Rubber instead of Night Blue?

The same difference applies the other way round: Black Rubber 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.