Iron Wolf vs Twilight Blue

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Twilight Blue is a little darker, warmer than Iron Wolf.

Can I use Twilight Blue instead of Iron Wolf?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Twilight Blue is a little darker, warmer than Iron Wolf.

Can I use Iron Wolf instead of Twilight Blue?

The same difference applies the other way round: Iron Wolf is a little lighter, cooler.

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.