Bluegrey Dusk vs Dark Sea Blue

How close are they?

ΔE 7.7, close: similar, with a visible difference side by side. Dark Sea Blue is more muted, cooler than Bluegrey Dusk.

Can I use Dark Sea Blue instead of Bluegrey Dusk?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Dark Sea Blue is more muted, cooler than Bluegrey Dusk.

Can I use Bluegrey Dusk instead of Dark Sea Blue?

The same difference applies the other way round: Bluegrey Dusk is more saturated, 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.