Marine Blue vs Thousand Sons Blue

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Thousand Sons Blue is cooler than Marine Blue.

Can I use Thousand Sons Blue instead of Marine Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Thousand Sons Blue is cooler than Marine Blue.

Can I use Marine Blue instead of Thousand Sons Blue?

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