Marine Blue vs Deep Blue

How close are they?

ΔE 8.4, close: similar, with a visible difference side by side. Deep Blue is more saturated, warmer than Marine Blue.

Can I use Deep Blue instead of Marine Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Deep Blue is more saturated, warmer than Marine Blue.

Can I use Marine Blue instead of Deep Blue?

The same difference applies the other way round: Marine Blue is more muted, 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.