Deep Grey vs Stormwolf Blue

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Stormwolf Blue is more saturated, cooler than Deep Grey.

Can I use Stormwolf Blue instead of Deep Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Stormwolf Blue is more saturated, cooler than Deep Grey.

Can I use Deep Grey instead of Stormwolf Blue?

The same difference applies the other way round: Deep Grey is more muted, warmer.

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.