Dunkelgrau RAL 7021 vs Dark Prussian Blue

How close are they?

ΔE 8.9, close: similar, with a visible difference side by side. Dark Prussian Blue is more saturated than Dunkelgrau RAL 7021.

Can I use Dark Prussian Blue instead of Dunkelgrau RAL 7021?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Dark Prussian Blue is more saturated than Dunkelgrau RAL 7021.

Can I use Dunkelgrau RAL 7021 instead of Dark Prussian Blue?

The same difference applies the other way round: Dunkelgrau RAL 7021 is 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.